Apparently thinking that Vincent’s lady friend…

Apparently thinking that Vincent’s lady friend would be a
more fun kill, Sebastian tries to drop her down the elevator shaft. That
doesn’t work because Vincent doesn’t let people hurt his Catherine, even if he
doesn’t remember her.
Vincent grabs her hand.
As he does, he has a flashback to other times he has rescued her in the
past: from being hit by a train, the first time he saved her, and of sitting
with her on her fire escape. He saves her from falling, before jumping down to
where Sebastian’s body is.