Part of the quest “Memory Interrupted”. The unmarked Police Department building beside it is one of the locations where you can get one of Eddie Winter's holotapes for Nick Valentine’s companion quest.
Station Interior
The red door to the right is chained so continue through the left. After going downstairs, there’s an advanced door to the north, beside the train. There’s a Fat-Man in front of the second train to the SE. The area have several Novice-locked suitcases.
Take the elevator to the NE to reach the lower area. There’s a generator with Fusion Core to the southeast.
Continue following the tunnel and you’ll eventually reach a large area where synths and raiders are fighting. Kill all hostiles, including a named raider Helter Skelter. There’s an issue of Tumblers Today under the duffel bag in the yellow train car to the NE.
The green steamer trunk is located to the southwest with a weapon workbench beside it. Mini-nuke is found among the pile of rubble to the right of the doorway of the exit. There’s also a cooking station in this area. Go through the other doorway then continue to the next elevator. This will take you behind the chained door. Unchain it and leave the area.