How Little We Know

 is a side quest in Fallout: New Vegas.

Walkthrough (NCR/House/Yes Man)
This quest is activated after talking to Yes Man (you can also talk to Joana after completing Bye Bye Love), once Bye Bye Love is complete, or by NCR after a few tasks during For the Republic, Part 2. Inside the main entrance to the Gomorrah, talk to the receptionist on your left. If it appears as a Speech option, ask her about "the outstanding balance" on information to find out what's been going on in Gomorrah. She will tell you to find Cachino, a low level lieutenant, and ask him about suspicious Omerta activities. If there is no "outstanding balance" speech option with the receptionist, ask a few of the dealers/bouncers/hookers about where you can find Cachino. With the Confirmed Bachelor perk a speech option will appear when talking to a male prostitute, giving you Cachino's location in Brimstone. If you have the Terrifying Presence perk, you get a new speech option and they'll tell you to meet him in Brimstone. They will all tell you to go away, but eventually Cachino will appear on the casino floor and talk to you. During For the Republic, Part 2, you will be asked to get some information regarding the Omertas by Colonel Moore. She will then tell the Courier to talk to Liza O'Malley to start this quest. The quest can also be given by Mick at Mick & Ralph's after asking him for work. He mentions that the Omertas have stopped buying guns from him without a word as to why.

Once the quest starts, you need to find proof of Cachino's work he's been pulling on the side. The Family doesn't know about this because it goes against Omerta rules, putting his life at risk if it ever gets out. There is a journal in his desk directly to the left as you enter the bedroom of his suite and another on his person that can be pick pocketed, this is the evidence needed. You can get the key to his suite from the receptionist for 300 caps, passing a Strength check of 8 (making it free of charge) or a Barter skill check of 55 (lowering the bribe to 200 caps), or pay the 300 caps, and pickpocket her to get it back. Once you return to Cachino and tell him you have his journal, he will offer you 100 caps to get the journal back, or if you have Barter of 60, get an additional 200 caps for his "friendship." He tells you about two people in the club that were brought in by the bosses as part of their plans and says to talk to Clanden and Troike about specifics.

Clanden will not give you any clues or talk with you about what he does at all, even if you mention that Cachino sent you. If you go back and speak to Cachino, he'll mention he did some asking around and the bosses' plans would be screwed if Clanden wasn't around, so he asks you to kill Clanden discreetly. Alternatively, you can steal Clanden's key off him which opens a safe located in his room behind the dresser next to the bed, or you can alternatively just pick the lock of the safe if you have at least 75 Lockpick skill. Taking the evidence within back to Cachino will result in him giving you the alternative to confront Clanden with the tapes. The key gained from pickpocketing Clanden can also be used to open one of the maintenance rooms on the suite level, where a dead hooker can be found (which you can investigate), and can be used against Troike.

When you speak to Troike, start asking about the dead hooker. If you have a high enough (35) Medicine skill you can say that the story he tells you about blacking out doesn't add up. The player can find evidence that there was foul play by looking for the blackmail note in a safe in Big Sal's Office that proves the bosses set Troike up. Alternatively, you can talk to Big Sal and convince him to free Troike from his contract with a high enough Speech (53) or Barter (45) skill, this allows Troike to be freed without having to investigate the dead hooker incident or find any evidence. If you have a Speech skill of 80, you can lie to Troike (giving you bad karma) and mention to him you'll tell the NCR of his dealing, bypassing the hooker investigation and talking to Big Sal. Alternatively you can present the Troike Blackmail Note to Marie Pappas.

Once Troike has been freed of his contract, he will cooperate and tell you about his involvement with the Omertas. He'll tell you he was smuggling guns in through NCR supply shipments, and you can discuss destroying the guns. He'll give you some thermite and a key to destroy the guns the Omertas have been gathering for their secret plans, or if your speech is high enough (70) you can convince him to plant the Thermite himself. The guns are behind a unique door in the hotel, with two footlockers containing a random assortment of flamers, sniper rifles, and assault carbines (these will help later in the next part of the quest). Place the thermite on the 4 crates of weapons and set off the detonator via the now active panel in the hallway near the closest door to the room. If Troike plants the thermite himself, he'll get caught and rat you out before the Omertas kill him, but this won't ruin any of your objectives.

After you speak to Cachino upon completion of both objectives, he'll tell you Big Sal and Nero need to be killed now. Luckily, they just put him in charge of finding out who's responsible for ruining their plans, and he'll lead you to a small room where the two bosses are. It is possible to convince Cachino to wait for your initiation signal with a Speech of 80 before the assassination. If you didn't get the guns from the room before you used the thermite, you can use the sawed-off shotgun Cachino gives you to kill the bosses, or you could use the holdout weapons you smuggled into the casino. Upon entering the room, the bosses will ask you to have a seat, and a conversation will begin. They talk about how they know you've been ruining their plans and how they want to kill you. At any point in the conversation you can start combat through a dialogue option, but it is possible with a Speech check of 80 to have Big Sal explain the whole plan to you and convince him that Nero was helping you. This results in Big Sal shooting Nero when combat starts. However, if you do this, Big Sal and Cachino will likely die very fast. Also, Big Sal and Nero can end up killing each other with one shot and the fight is over. If you want to avoid combat, you can quickly loot the office key from Big Sal and run outside. The various Omerta Thugs in the casino will kindly assist you with killing Nero.

Once the bosses are dead, the quest is complete and Cachino will take over the casino. If you speak to him after the fight he'll offer you 50 Gomorrah tokens as thanks.

More ways to quickly finish the combat. 1)A very simple way to kill them quickly is to use the sniper rifle you obtained from the weapons cache room or with a silenced holdout weapon. Let Cachino go into the room but don't go in yourself. Find a position where you're able to get a clear shot of Nero/ Big Sal and take him out, then do the same for the the other. Killing them one at a time does not initiate hostility as long as you are hidden when you take the shot. This will result in completion of the quest with no negative karma/fame. 2) If you have Arcade Gannon as a companion, simply give him the flamer and some flamer fuel. The bosses should be burned to death rather quickly as they only focus on shooting you. 3) Similarly, if you have Veronica as a companion, make sure you bring in special unarmed weapons such as Love and Hate or Pushy. They should pass the security check with no problem. Arm her with that and she'll take care of the rest rather quickly.

Alternative Solution (Legion)
If you inform the guard at the door to the Zoara Club that you have proof that one of their guys is dealing on the side, he will let you in to see the bosses. You can talk to Big Sal and offer him Cachino's journal for 100 or 200 caps if you succeed in a Speech check. After that, everyone is brought into Big Sal's office for a meeting where Button Man will kill Cachino after he begs for his life. Talk to Big Sal afterwards, he'll ask you to take over for Cachino then offer you a job aiding Clanden and Troike in their plans.

For Clanden, it means helping him kill "a large amount of people in a short amount of time". If you have a high enough Science skill (60), you can persuade Clanden into making a Chlorine Bomb easily, otherwise Clanden will tell you what is needed. Chlorine can be stolen from the Ultra-Luxe casino, or purchased from Ralph in Freeside. The Chlorine from Ultra-Luxe is found in a small supply closet with an Easy lock on it, in the area behind the counter where Mortimer is. You can also persuade Ralph to give you Chlorine for free by passing a Science speech check of 60.

Troike will tell you that he is a gun smuggler and inform you that he needs someone to retrieve a crate of guns stolen by the Fiends. The location will be marked on your map, guarded by 4 Fiends. Once you retrieve the disassembled weapons shipment, return to Troike.

Once the Chlorine is given to Clanden and the weapons to Troike, you will then be told to see Big Sal. Upon informing Big Sal of having fulfilled his request to aid Clanden and Troike, he rewards you with 400 caps. You can also speak to him about 50 Gomorrah tokens. Choosing this solution will cause the player to lose fame with the New Vegas Strip, and during the Wild Card: Side Bets quest, a dialogue option will appear when talking to Yes Man saying that you support the Omerta's plans of attacking and taking over the strip.

Bugs

 * If you don't speak to Liza O'Malley before starting How Little We Know then you will not be able to speak to Cassandra Moore upon returning to Hoover Dam. As such, you are unable to complete For the Republic, Part 2
 * If Boone has the unique weapon The All American, upon exiting the building, he will not have the weapon returned
 * If you attack the dead bodies of Big Sal and Nero after killing them, you will continue to gain experience. This can vary from 50xp to 750xp each hit.
 * When speaking to Cachino before going to kill the bosses, selecting the "Wait" and "Ready" dialogue options may prevent Cachino from further interacting with the player. When trying to re-initiate dialogue, Cachino will only respond that 'there is no time to talk' meaning the player cannot tell him they are ready to go; and he will also remain in place and not lead the player to the meeting with the bosses, preventing further progress in the quest. Leaving Cachino there and attempting to finish to quest later will revert Cachino to previous lines of dialogue in which you can only ask about the bosses' plans, Troike, and Clanden. Note: this quest was undertaken before initiating or completing Bye Bye Love as the walkthrough indicates is necessary. It is unknown if this is related to the glitch. (Update, 360): Completing Bye Bye Love does not unlock communication with Cachino.
 * This bug can be bypassed, by simply finding the small office where the meeting would take place (next to Big Sal's office on the main floor) and killing the bosses, resulting in a quest complete message, regardless of Cachino following you there.
 * It is possible to fix this by taking the elevator to the main floor, then typing "prid 11118d" followed by "moveto player" in the console to bring Cachino to the main floor. Once Cachino gets to the main floor, he walks normally to the bosses' room and the usual sequence of events proceeds.
 * When Cachino is supposed to give you the double-barreled shotgun, it may end up in your companion's inventory instead of yours. This can occur even if Cachino is still bugged as previously mentioned.
 * Sometimes, after planting the thermite charge, the switch won't set off the explosives.
 * If you steal Sal and Nero's ammo before sitting down for your chat, choosing the lie option implicating Nero will cause the two of them to stare at one another with guns out, but they will not attack due to lack of ammo.
 * If you accidentally start a fight with the body guards or security, then exit the Gomorrah to The Strip, when you re-enter the casino, the game freezes and your character can look around, but is unable to move. On PC (as of patch 1.2.0.285) the game will freeze if re-entering the Gomorrah after your refusal to surrender your guns to guards before entering.
 * Possibly fixed in patch 1.2.0.314. Needs confirmation.
 * You can use the command EnablePlayerControls to fix this on the PC version. In this one instance, the Gomorrah guards will not ask you to surrender your weapons. Meanwhile, with this bug, your companions may or may not enter the casino with you. If The House Always Wins is already started, then you will likely find them in the Lucky 38 Presidential Suite. Otherwise, they have likely returned to their starting places.
 * The dead prostitute you can inspect during "How Little We Know" can be found alive and standing before, during, or after the quest is complete. If you examine her the box telling you to inspect her will still pop up.
 * If you receive the key from the receptionist, you can lift the book off Cachino AND head up to his room to get another copy of his journal. Sell the first one with the Barter check then talk to him again for the 100 caps and intel on the Family's activities option.
 * After receiving the option from Cachino to kill Clanden, occasionally, killing Clanden will result in a failed mission. In this play-through, Troike set off the thermite and didn't know he was exonerated. It is unknown if this triggered the bug.
 * If the player chooses to bypass the quest and instead simply kill the Omertas, Big Sal may not necessarily become hostile. it is possible to approach him after fighting through the rest of the main floor and pass the Speech 50 check to convince him to buy from Mick and Ralph's, even though in the context of the game this is a complete non sequitur. You also have the option to get 50 chips from him. This will also advance For the Republic, Part 2 and prompt the player to lie to Colonel Moore even if the Omertas have been eliminated.
 * If the player has chosen to assault the Omertas and kill them all, ED-E may kill one of the unnamed prostitutes in the courtyard.
 * If you side with Cachino for this quest, then go talk to Clanden without having the evidence to progress in dialog, then see Troike and finish his objective, reporting back to Cachino will cause him to tell you that it's time to take out the bosses, bypassing Clanden's portion of the quest altogether.
 * Sometimes, after completing "How Little We Know," you can't tell Mick that the Omertas are buying his weapons again. To work around this, before telling Troike to destroy the weapons, have his contract destroyed by talking to Big Sal before completing the quest. Then tell Troike he is free and then tell him to destroy to the guns. Note that if you find the Troike blackmail note before talking to Troike about the prostitute, although Troike will still have the dialogue asking for help getting out of his contract, Big Sal will not have the related dialogue, so you cannot get Troike out of his contract, thus never tell Mick that the Omertas are buying guns again, and thus never get the Pimp-Boy 3 Billion.
 * The dialogue option that starts this quest can appear without doing "Bye Bye Love" or starting "For the Republic, Part 2", for no apparent reason.
 * If you completed this quest and have a companion with you, all of your companion's inventory items may be removed, even their default weapons. I was being followed by Lily, who was carrying 100 lbs. of equipment. Now she uses unarmed attacks in combats and has no ranged weapon. Additionally, that equipment she was carrying was worth over 10,000 caps. This also may happens with Arcade and ED-E.
 * There are known issues with bringing companions into the casinos and having their inventories altered by the weapons check.
 * Killing Clanden may cause ED-E to stop following the player (it just gets stuck). Making ED-E wait won't help. Ordering it to return to base, then quickly killing Clanden and rehiring ED-E will help. The same thing may happen when killing Big Sal and Nero.
 * If you proceed with killing Cachino and beginning the missions for the Omertas family, the receptionist that Mr. House sends to speak with you during The House Always Wins, Part 4, may not give you the necessary speech options.
 * After talking to Big Sal and telling him of Cachino's treachery, going into his office to have a 'little talk', button man remains immobile, Cachino just sits there and none of them will speak with you anymore. Still looking for fix.
 * After picking up the blackmail tape, you cannot negotiate Troike's contract with Big Sal. This means you cannot free him and get the Pimp Boy. At this stage, you also cannot turn in Cachino, as he will have his diary back (pickpocketing it does nothing) meaning there is no way to get the Pimp Boy at all. To get around this the courier must kill Cachino then talk to Big Sal who will buy the guns from Mick and Ralph if the courier selects the 50 speech check. Doing this will fail the mission but grant the player the Pimp Boy after talking to Mike.

Behind the scenes
"(How Little It Matters) How Little We Know" is a song written by Carolyn Leigh and Phil Springer, and recorded and released by Frank Sinatra in 1956.