Without a Trace (1983)

"One morning, Alex Selky got dressed, waved goodbye to his mother, set off for school and disappeared."

English professor Susan Selky lives alone in a Brooklyn apartment with her young son, Alex. When Alex fails to return home from school one afternoon, a frantic Selky contacts the police. Detective Al Menetti, a father himself, takes an interest in the case that quickly turns into an obsession. As a devastated Selky struggles to come to terms with Alex's disappearance, Menetti steps out from behind the badge to continue investigating.