And yes, Chris does resign after the Mansion Incident. I just said that. When they return from the Mansion, in the next few days, Chris tries to get background reports and files on Umbrella. He also starts a research time, but Irons sabotages it.
Chris tehn acts around loosely, punching one of the members in the mouth for spilling coffee on him, and then everytime he did something, he would smile at Jill. Which Jill would not understand.
Then, the day he resigns, the RPD loses all contact with Chris.
Soon after, Jill resigns, with Barry. And then she sets to find Chris, but he has already left to Europe. RE3 happens. Barry comes gets her. They both go to Europe after Chris.
That's a small summary.