When Freedom Calls

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

Detailed walkthrough
During travels through Concord, the Sole Survivor will spot a man protecting a group of people from Raider attacks on a balcony of the Museum of Freedom. Below the balcony is a short laser musket and some fusion cell ammunition in front of the doors. Pick it up if interested in disintegrating the enemies, and clear any foes from the streets before entering the Museum.

Fight your way through the raiders and head upstairs. On the second floor, meet Preston Garvey and the remnants of his Minutemen forces. While here, be sure to pick up the Perception bobblehead and the RobCo Fun magazine, containing the Atomic Command holotape. Agree to help him and Sturges provides fire support to crush any remaining Raider opposition in town. Drop to the ground floor and into the basement. From here, one can choose to either hack the terminal to unlock the door or directly pick the lock; both are of novice difficulty. Either way, once having opened the door, grab the fusion core inside.

Having acquired the fusion core, head upstairs and onto the roof to find a suit of T-45 power armor. Insert the fusion core into the power armor and climb inside the suit. From here, one can take the minigun from the vertibird. One can either jump off the roof, or stay on it for a little while. Either way, start killing the enemies on the ground. When killing Gristle, the only named raider, be sure to pick up the Corvega storage key from his body. Once having killed a considerable number of raiders, a deathclaw will spawn. Although it looks menacing, it is relatively easy to defeat with both the minigun and the power armor. The deathclaw can do a lot of damage however, so be cautious. Once having defeated all of the enemies, enter the Museum of Freedom and speak to Preston Garvey to complete the quest.

Bugs

 * Preston Garvey won't talk to you after reaching Sanctuary, the quest cannot be finished.

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