Use Mark as 1st partner. Request the Magazine from Mark when started. Get the handgun bullets at West concourse. Go to East tunnel and get the password. Go to Men's restroom (east) to get and equip the Handgun before you leave. Shoot the door of East concourse with 19 shots of Handgun. At the Employee passage, there are 2 zombies. Avoid them or use spinner to knock them down. Enter the Control room to get the file. Zombies will get in. Wait them to come in before you leave. If you have time, combine the bullets and magazine. Back to the Employee passage. Shoot the door of Employee passage near the Emergency power room with 19 shots of Handgun. The break room has 1 zombie. Unlock the locker in Break room and get the B2F Key. Avoid the zombie or use spinner to knock the it down. Run to the Emergency power room and get the Valve and the Shotgun. Equip the Shotgun before you leave. In B2F passage, if the zombie block your way use spanner to crash them down. When entered Pump room, aim to the door. When the zombies come in, shoot to their head. After kill the zombies, use Valve to stop the leaking. Repair the tube by using David's repair tape. Restore the water system again with Valve. (Some Zombies will break in again, watch out your steps) Get the Shotgun shells at the corner. Get the Emblem on the ground. Back to Emergency power room to enable the power. Enter to the Breaker room to restore the power. Unlock and get out the Employee passage from the west. Get close to the train in platform to activate the "Mega Bite" event. Use the Emblem beside the train. Get the Bug spray on the railway. Go to the opposite side of the platform and wait the train arrived. Be careful of the "Kilo Bite" just kill them when they get close. Wait the train crash. (reload your weapons) Get the other Emblem and use it. Get into the train and get near to the controller. The "Giga Bite" will capture you. Kill the "Mega Bite" with 2 shoots of Shotgun. Kill the "Giga Bite" with Bug spray. (aim to its head) Get back to the train and wait to complete this scenario. ... https://www.youtube.com/watch?v=p--ZDsWNjvc

Start: Entering the train End: Scorpion boss ... https://www.youtube.com/watch?v=hu_JTZKgyD4