Poor Leonard is not having a good time; he, unlike Helen, hasn't been able to intellectually process their affair. He's full of remorse.
Leonard never once imagines that it might be Helen's fault, or that they might at least share the blame. We, however, see that she is just as responsible as he was, or perhaps more – she loves things that are absolute, and Leonard's total destruction appealed to her.
The morning after their tryst, Helen was gone. She left a note that meant to be kind, but broke Leonard's heart; he felt immediately terrified and guilty, as though he'd ruined her.
The trip to Evie's wedding really destroyed the Basts financially. Helen, in her fit of passion, forgot to pay the hotel bill, and also ran off with their return train tickets. Despite all of her talk about being responsible, we see that she was really careless, selfish, and destructive.
Leonard, desperate, was forced to ask his estranged family for money. He succeeds in wheedling some cash out of his two sisters and their husbands, but this just makes them hate each other more.
The only things that keep Leonard alive are his sense of really living, even if it means suffering, and his affection for Jacky. He seems to view her as a kind of pathetic animal who needs care; this sense of duty keeps him going.
One day, Leonard sees Margaret and Tibby from afar. He wants to come clean and tell them everything – he trusts Margaret, and decides that he must talk to her. He figures out where she lives, and stops by Ducie Street.
Leonard finds out from the maid, who finds out from Tibby that Margaret is at Howards End, in Hilton.
Leonard stays awake all night thinking about his confession. He's tormented by his imagination, and eventually gets up to go out, telling Jacky that he'll be back soon.
Leonard takes a train to Hilton overnight and reaches his destination in the morning. He feels more alive and optimistic in the countryside, far from the artifice of the city.
Leonard reaches Howards End, and finds himself with Margaret and some other people. He is totally disoriented and confused – and is attacked by a strange man, who grabs him by the collar and says that he's going to thrash him.
Confusion and violence ensues; Leonard is attacked by a bright stick, then collapses under a falling bookshelf. It's chaos.
Charles, the attacker, declares that Leonard is faking – but, in fact, he's dead. They carry him outside.
Margaret and Helen don't understand at first – they pour water on him, hoping to revive him. Miss Avery comes out and says that Charles murdered Leonard.