- "Sometimes I worry about you, Bevvie. Sometimes I worry a lot!"
- ―Alvin's most common catchphrase
Alvin "Al" Marsh is the widowed spouse of the late Elfrida Marsh and the insane, abusive father of Beverly Marsh in the Novel It. Like Butch Bowers (Henry's dad) and Eddie Corcoran's stepfather, Richard Macklin, Al occasionally abuses his daughter. Unlike Butch and Richard, he tends to beat and abuse Beverly for odd reasons, even though he doesn't smoke or drink (which are often the two key elements of child abuse). While beating her, he constantly tends to say "Sometimes, I worry about you, Bevvie, sometimes I worry a lot."
He abuses Beverly and her mother (who later died) and acts misogynistic. He hates it when she hangs around with boys. He is also a form that It uses to frighten Beverly, since she is afraid of him. In the novel and the miniseries, he dies of unknown causes, possibly he was eaten by It. In the 2017 film, however, Beverly kills him whilst he attempts to beat her. It is also heavily implied in the novel that he was sexually attracted to his own daughter.
However, there are times when Al proves to be very loving and affectionate towards Beverly. He died from unknown causes in 1980. He also appeared as one of It's manifestations, taunting Beverly into getting out of Derry.