Tunnel Snakes Rule!

Tunnel Snakes Rule! is a side quest

Walkthrough
Listen to the faint radio signal to be directed to the Fens Way station. Navigate the area to a door to the subway maintenance access. Enter through a Novice locked door, and through one of two arched doors in the wall to find what appears to be an abandoned camp. Clear this section of the metro tube and continue back right to be ambushed by a feral ghoul who crawls out behind some scaffolding ramps and another feral who appears to be sleeping on a bed.

What remains of Wally Mack, who is now a glowing one, comes down from the top of the scaffolding ramps. once killed, Wally Mack drops Ultimatum, a unique Classic 10mm Pistol that does 50 radiation damage on top of having a unique model no other weapon or item uses.

Bugs

 * When the Sole Survivor goes to Concord, one of several glitches can happen with both this quest and Out of Time active:
 * The quest may prohibit Codsworth from searching the neighborhood, with his last line of dialogue bugging out.
 * The dialogue with Preston Garvey may bug out after the door inside the Museum is unlocked.
 * Entering through the door to enter the roof may not be possible.