what was the movie with martin mull in which he had to rescue his daughter from a cult

The movie is Serial (1980). Martin Mull’s character tries to rescue his daughter from a cult, with help from a motorcycle club.

Quick scoop

• Title: Serial.

• Plot clue: it ends with Martin Mull’s character rescuing his daughter from a cult.

• Release era: early 1980s.

Why this fits

That exact “daughter from a cult” detail matches the discussion around the film, and the cast/title listing lines up with Martin Mull being part of the movie.