Just when they think the trip to the lake will happen, it doesn't. Angry Lolita refuses to go to church and so stays home with Humbert.
Humbert gets really cozy with his reader here, wanting to make sure that we don't think that he's a pervert because of the story he is about to tell us. As he often does, Humbert lays out the events like he is describing a scene in a movie.
This is what he tells us:
He and Lolita are sitting on the couch engaging in some highly symbolic extended flirtation involving an apple. While Lolita moves around on the couch fighting over a magazine with Humbert, he derives secret pleasure from her body's movements near his.
Humbert describes his private climax in highly poetic terms. Lolita doesn't even appear to notice that he has just had achieved a "euphoria of release" (1.13.12), and trots off in her silly way.