Cephas recounts the story of the forbidden love between Tommy Cox, who has an intellectual disability, and Sarah Warren, the underage darling of polite society. The two are pushed together by a mysterious illness, and their resulting illicit relationship results in a heated trial that stirs the entire town. Tommy's prosecution turns on whether he could have, under the law, formed the requisite intent to be found guilty of the crime for which he's charged. Cephas and his friends-Lump, Brett, and Michael-struggle to come to terms with their growing knowledge of Tommy and Sarah's intimate relationship. Along the way the four learn much-perhaps too much-about justice, truth, lust, and love.