Guess Who I Saw Today

 is a quest in Fallout: New Vegas.

Quick walkthrough

 * 1) Go to Jacobstown.
 * 2) Speak with Doctor Henry.
 * 3) Head to Charleston Cave.
 * 4) Retrieve the Chewed Stealthboy.
 * 5) Return to Doctor Henry.
 * 6) Talk to Lily Bowen.
 * 7) Deal with Keene.

Detailed walkthrough
To begin the quest you must go to the Jacobstown Lodge and talk to Doctor Henry and tell him you will help him with a problem.

Meet with Lily, a smaller Nightkin standing by the pen outside the front of the lodge after accepting the quest. You can invite her to come with you, but do not have to (This will only work if you do not have a fellow humanoid companion already).

Exit Jacobstown and circle around to the Northwest to locate Charleston Cave, and enter. Continue through the cave following your compass (generally moving downhill) while dispatching Nightstalkers and eventually you'll come across a couple of Bighorner bodies and a Nightkin body, with Oh, Baby! next to it. Examine the Nightkin and take his Chewed Stealthboy and you'll be prompted to return to the Doctor Henry back in the Jacobstown lodge.

Back at Jacobstown, talk to the doctor. He'll inform you that the Chewed Stealthboy may be a breakthrough in his research and that Lily is his best experimental subject. Talk to both the doctor and Lily, they both will agree to the experiment. It's a success, but as soon as the doctor is finished Keene enters the room and demands the Stealthboy Mk. II specs.


 * If you can pass a speech check (80), Keene can be spoken down.
 * If you give him the specs he'll leave.
 * If you don't give him the specs, he and two other Nightkin will attack.
 * You can easily draw the three of them outside and let the Super Mutants help you do your work.
 * You can also go in the corner (where the wheeled tables are) to prevent the Nightkin from attacking you (or delaying them).
 * It is possible to use a Stealthboy and reverse pickpocket C4 onto Keene and his 2 Nightkin before speaking with him. This way, if you chose to fight them, you can use a detonator to instantly kill all 3 at once.
 * Note, Lily will leave the lodge as Keene is coming into the room, she will therefore not help you with the fight**

In the lodge, speak with Doctor Henry again.
 * If you can pass a science check (90) you can convince Henry to test the Stealthboys on Nightstalker brains.
 * You can also inform the Doctor the risk is too great, and Lily should not wear it.
 * You can also tell him you think Lily should continue to wear the Mark II prototype.

Whichever decision you choose, it will end the quest. The outcome of each decision seems to have a different effect on the game although you will always be able to take Lily as a companion ✅. Passing the Science check gives you around 100 more experience than the other two options do. Passing with the science check awards 590 XP.

No matter the outcome, the player will NOT be able to acquire the Stealth Boy MK II Prototype.

Bugs

 * After initiating the Mk. II test on Lily, if Calamity is not present in the room (such as sleeping), there will be a long pause in the dialogue when Doctor Henry asks for the results and Calamity's words will not be spoken.


 * If you enter the lodge after talking to Lily and then initiate the test before she enters, she will either remain outside, invisible, or she will run over to Doctor Henry and neither of them will talk to you when prompted. This may be fixed by pick pocketing Doctor Henry, but doesn't always work.


 * After you give Doctor Henry the chewed stealth boy he will not experiment with Lily and the quest will be stuck. (So will the quest For Auld Lang Syne as you will not be able to recruit Doctor Henry). Lily will continue to say that she is helping Doctor Henry and neither will allow you to progress. This can be fixed by killing Lily as she stands against the wall (she won't attack), and then approaching Doctor Henry, in which he will give you his pass-phrase for the "For Auld Lang Syne" mission. This will disrupt the "Guess Who I Saw Today" mission.

An alternative to this is to 'wait' in the doctors office while the quest is stuck (Lily invisible and Doctor Henry just standing there), let the game save and proceed to kill Lily. Afterward, talk to Doctor Henry; you'll then have the dialog option to give him the chewed Stealth Boy again. Once the dialog is chosen, he'll take the device and proceed to tell the Courier how he had a plan to experiment the Mk.II Stealth Boy on Lily, but she's dead. You'll then fail the quest and receive 550 XP. Exit the dialog and then reload the game, this continues the game from the saved 'wait' point with no bugs attached.


 * When the quest is stuck with Lily invisible and you have ED-E as a companion, you may target Lily in V.A.T.S. and after exiting it she will no longer be invisible. However, the quest will still refuse to proceed.


 * After you've killed them, some of the dead nightstalkers in Charleston Cave are still standing/sitting as if they were alive.(This bug is very common with other four-legged animals/mutants such as: Bighorners, Brahmin, and Vicious Dogs.)


 * After telling Lily to return to Jacobstown from The Lucky 38 (she was not a current companion at the time) she disappeared. Fast traveling to Jacobstown and talking to Henry progresses the quest as normal, but he will ask the absent Lily to use the prototype and proceed to hand it to nothing but air. He will then simply stand there and nothing will happen. Waiting has of yet, not fixed this.
 * Waiting 24 hours made Keene appear in the room with two other Nightkin. Speaking to Keene progressed the quest, but Lily is still nowhere to be found.


 * For some reason, after Lily has just powered down the Stealth Boy Mark II, Keene will instantly run into the room and become hostile. This will also make every one (Doctor Henry, Lily, Calamity) in the room hostile against you and you followers. It will then say "Quest Failed" despite the fact that you didn't even talk to Keene