Time passes. Posy is born, daughter of Tim and Mary. We are at a party, possibly the child's first birthday. They are awaiting the arrival of aunt Kit-Kat, but her boyfriend Jimmy arrives alone. He had had a fight with a somewhat intoxicated Kit, who left to drive herself to the party and seems to have taken an unintended detour to an emergency room via ambulance.
Tim does the obvious: he travels back a few hours and drives over to bring Kit to the party himself, arriving late and excusing that with the claim that someone told him she would not be fit to drive herself. Thus he prevents the accident, but he remembers it, and it motivates him to do something to change Kit's life. Others agree that she needs help, based on her excessive drinking. The problem, he decides, is Jimmy.
We learn something else about this time travel ability, something that neither we nor Tim had any reason to expect would work and probably of which none of his progenitors were aware: if he holds someone's hands he can take them with him to the past. This changes our perception of what is happening significantly--there is no reason to think that the ability to slip out of your body in the present for an instant during which you make significant alterations to the actions of your past body and then return to your future body would include the ability to take this passenger who would similarly slip out of her present body and into her past body and return with you, simply because the present bodies are in physical contact with each other in the same space. Yet he attempts it expecting it to work, and succeeds. He thus takes Kit back to that same New Years Eve party at which in one sense it all started.
Getting past the part about returning to the same moment again, we find that the same principle that apparently applied to Mary (you will fall in love with someone when it is the right time) also applies to Jimmy, whom Kit sees pick up someone else at the party when she is not in the right place. We might complain of the double standard, that it was a fortuitous thing with Mary but a vice when it was Jimmy, but Jimmy does seem to be a creep, and Kit immediately guarantees that the creep who never loved her never will--she clobbers him and storms out to return to the future.
We again have that problem that things change but our time traveler seems to replace the version of herself who would have remembered the change--she is apparently living with Jay in this timeline. We never learn how that is working, though, because when Tim gets home and pulls Posy out of the high chair, she's a boy. This was the butterfly effect problem of which his father was apparently aware but failed to mention, and it is only one of the several complications that arise surrounding this trip and the next, which we will address next time.