Thank you for clarifying the chapter, as the chapter numbers for Love Medicine changed after Louise Erdrich revised her novel.
The climax of the novel has to be the moment when Nector Kashpaw dies. Everything before this moment leads us to believe, as the title suggests, that the "love medicine," which Marie Kashpaw has placed her hopes in and which Lipsha Morrissey has told her he can accomplish, will effect a change in Nector. It does, of course, but not the change anyone was hoping for.
Early in the chapter. Lipsha describes his grandfather this way:
He was a hard nut. You know, some people fall right through the hole in their lives. It's invisible, but they come to it after a time, never knowing where.
In this chapter, Nector Kashpaw, at an unexpected time and mostly through his own doing, falls through the hole he made in his own life.
Lipsha has had to create a false love medicine, using frozen turkey hearts he bought at the store instead of the goose hearts he wanted to use (because geese mate for life). When he presents them to his adoptive grandparents, Marie eagerly eats the raw (what she thinks is female) turkey (what she thinks is goose) heart. Nector, however, cannot be persuaded or tricked into eating the raw heart, turkey or goose.
Instead, in an effort to taunt and goad his wife even further, Nector places the whole heart into his mouth and rolls it around but refuses to swallow it. This is infuriating for the hurt, angry, and rather desperate Marie, and she slaps him hard on the shoulder blades, hoping this will make him swallow the fowl heart. Instead, he chokes on it and dies.
Lipsha, the one with "the gift," is unable to revive him. His gift does not work on his grandfather, just as Lipsha said it would not at the beginning of the chapter. Even more, Lipsha's gift has left him. This, too, is part of the chapter's climax.