Sometimes They Come Back is a novelette by Stephen King, first published in the March 1974 issue of Cavalier and later collected in King's 1978 collection Night Shift.
Synopsis[]
Two brothers are walking to the library when they are attacked by a gang of local greasers. One brother is killed while the other gets away. Many years later, Jim, the survivor of the attack, takes a job as an English teacher at a high school. Students from his class are murdered and are replaced by students that resemble the greasers that attacked him years before.
As it turns out, the greasers were killed in a car accident after they attacked the brothers. They have been brought back to life to finish their business with Jim. After they kill his wife, Jim uses a ritual to summon a demon (taking the form of his slain brother) to kill the greasers. Because he deals with the powers of darkness, things turn out less well than he had hoped. The ending implies that the forces he summoned to dispatch the greasers may also be just as sinister, and as difficult to get rid of as the greasers themselves were (the demon posing as his brother states "I'll be back, Jim").