When Freedom Calls

When Freedom Calls is a Minutemen main quest and achievement/trophy in Fallout 4.

Detailed walkthrough
As the Sole Survivor enters Concord, they will hear a commotion around the Museum of Freedom. A group of raiders are laying siege to the building while a man on the balcony fires back with a laser weapon. To begin the quest, the Sole Survivor must help eliminate the raiders outside of the building. With the threat neutralized, the man on the balcony will call out to them with instructions to grab the short laser musket and fusion cells on the ground and use them to help fight off the raiders inside the building.

Once inside the building, the Sole Survivor will find themselves under fire from raiders on the balcony directly ahead. There are two pathways forward including a series of museum exhibits to the right and a gate with an Advanced lock below the balcony. Both pathways lead to the other side of the balcony, where a stairway and a collapsed floor grant access to the second floor and basement, respectively.

Climbing to the second floor, the Sole Survivor will find a ruined office area on the southwest side of the building. A door on the northeast side leads to another series of raider-infested exhibits, which then lead into another stairwell to access the third floor. After exiting onto the upper balcony and eliminating the remaining raiders, the man from outside will open the door at the northwest end of the balcony leading into the building's main office.

As the Sole Survivor enters the office, the man will compliment them on their timing and introduce himself as Preston Garvey of the Commonwealth Minutemen. After introducing the rest of his group Preston will turn the conversation over to Sturges, who will lay out his plan to deal with the remaining raiders in Concord: steal the "cherry" suit of T-45 power armor in the pre-War vertibird embedded in the building's roof, then wipe the raiders out with the vertibird's minigun. There is just one small problem: the armor needs a fusion core to power it, and the only working core in the building is locked behind a security gate in the basement.

In the office, the Sole Survivor can find the Perception bobblehead and a copy of RobCo Fun containing the Atomic Command holotape. Mama Murphy will stop them to talk about the Sight and offer a cryptic warning: something is coming, and it is angry. Passing a moderate Charisma check will encourage her to speak of something very dangerous that will rear its ugly head during the coming battle; failing the check she will simply respond "It ain't a raider." The Longs will spout some panicky dialogue, but will not reveal any useful information.

From here the Sole Survivor can head to the basement to tackle the Novice locked terminal or the Novice security gate and retrieve the fusion core. With the core in hand, they can then head to the roof to retrieve the power armor and minigun, as well as a holotape from one of the crash victims. The raiders will quickly spot the Sole Survivor as they grab the minigun. Alternatively, the Sole Survivor can skip all this and head straight outside.

As the Sole Survivor engages the raiders, loud banging noises will emanate from the sewers, warning of things to come. Once enough time has passed or the Sole Survivor approaches the end of the main roadway, a deathclaw will burst out of the sewer and begin attacking everything it sees. The minigun can be used to eliminate these threats while using the nearby buildings for cover.

After clearing the area of hostiles, the Sole Survivor can re-enter the museum to find Preston and his group ready to move out. Preston will be awed at the Sole Survivor's display, and reward them with 100 caps and 50 fusion cells before discussing his intention to move the group to Sanctuary Hills. Mama Murphy will then bring up the Sole Survivor's destiny, revealing that she can feel their son's energy but does not know exactly where he is. She will suggest to the Sole Survivor that they head to Diamond City to seek out more information, starting the next quest, Jewel of the Commonwealth. After wrapping up the conversation, the group begins traveling to Sanctuary. The Sole Survivor can travel with them or meet them there later to complete the quest.

Companion reactions
Preston is upset about the decline of the Minutemen during his initial meeting with the Sole Survivor

Preston asks the Sole Survivor to clear out the Raiders using the minigun on the roof

Sturges asks the Sole Survivor to retrieve the fusion core from the basement

Mama Murphy is musing that Dogmeat was a good dog for bringing the Sole Survivor to the museum

Mama Murphy calls the Sole Survivor their hero

Mama Murphy foreshadows that something angry is coming

Preston says he's glad to have the Sole Survivor on his side after the Deathclaw is wiped out

Preston asks the Sole Survivor to help them out at Sanctuary

Bugs

 * If the player character forcibly breaks out of conversation with Preston after defeating the deathclaw but before letting Mama Murphy's dialogue initiate the Jewel of the Commonwealth quest, it can break the quest. Preston and the rest of the settlers will speak as if they are currently en route to Sanctuary, but will never leave the museum. This effectively locks the player character out of all further Minutemen quests, as even using the console to complete the related quests will not update Preston and the rest of the group, and they will remain permanently "stuck" in their journey to Sanctuary.
 * It is possible to break this quest if the player character ignores the raider battle and instead rushes to engage the deathclaw, resulting in Preston remaining on the balcony with no dialogue options. Using the console and the command will not fix this issue. Although it seems intuitive that the destruction of the deathclaw should trigger completion, using  on the deathclaw and killing it again may not advance the quest. Instead,  and kill Gristle. This will trigger Preston's dialogue, and he will then leave the balcony and the quest can be completed.
 * It is possible to fix this by heading to Sanctuary, teleporting Preston there by typing in the console. Preston will then start moving back to the museum, but can be spoken to, exhausting his dialogue advances and completes the quest.