First, kill the giant bug in the East Tunnel. Then choose of these endings:
1- After killing, ride the subway train.
2- Let the train go, and it will leave a key. Use the ventilation key at the locked door.

SAVE YOUR SELF DONT WORRY ABOUT FRIENDS!!!!!!!!!!!!!!!!!!!!

Get Red Tag key. Open Staff door. Get file in control room. Get file in men's staff
toliets. Open locker and get B2F key. Unlock door. Go to room wth generator. Get Valve
Handle. Use it in Pump Room. Use it. Get Werner's head outside room. Put it in slot
between train. Go to breaker room. Turn on power (All digits adds to 10, like 1 to 9, 2 to
8, 10 to nothing) Go in Storage room. Get Vinyl Tape. Use it on crack on pipe. Use Valve
Handle, then discard it. Go to platform. Wait for 2nd train to crash. Get Oral head, and
put it between train. Go on train, after killing big flea. Watch partner/you taken by big
flea. Go down hole opposite train. Kill HUGE flea with A. Rifle or Shotgun. Listen to
train departure warning, and get on train!! If miss, get Ventilation Tower key. Go to
generator room. Use key. Get Turning Wheel. Use it. Get to the top!!!