Follow the vault girl through the ruins and remember to stay close to her. You're slowly losing health from the gaping hole that was once your left arm. Note that your actions are limited - you cannot run, jump, or use two-handed weapons.
After being throw into the abyss by Attis, the Initiate is woken up by Mary. Follow her through the maze of ruins. Because of your injuries, you're incredibly slow and steadily losing health. Use stimpaks to prevent your health reaching 0. Mary takes off, but if she gets too far ahead, she waits for you. As if the wound isn't enough to slow you down, radscorpions and baby deathclaws attack from every angle. Smash them using one-handed weapons (you only have one hand, remember?) and continue to follow Mary until you reach the last door. As Mary urges the other side to open it, the Iniate faints and wakes up in the Facilities' medical bay.