Cast of The Manhattan Project

John Lithgow portrays John Mathewson, a nuclear physicist overseeing a top-secret project involving a high school student and a homemade atomic bomb.

Christopher Collet plays Paul Stephens, the high school student who decides to build a nuclear bomb for his science fair project.

Cynthia Nixon takes on the role of Jenny Anderman, a friend of Paul's who gets caught up in the dangerous experiment involving the atomic bomb.

Jill Eikenberry portrays Elizabeth Stephens, Paul's mother who becomes concerned as she uncovers the truth about her son's project.

John Mahoney plays Lt. Col. Conroy, a military officer involved in investigating the potential threat posed by the homemade nuclear bomb.

Richard Jenkins portrays the Radiation Controls Officer, a character responsible for assessing the safety and risks of the nuclear experiment.

Robert Sean Leonard appears as Max, a friend of Paul's who becomes entangled in the dangerous scientific project involving the atomic bomb.

Steve Blum is credited as portraying the Laser Efficiency Kid, contributing to the scientific aspects of the project with his character.

Sarah Burke appears as Jenny's Parent, a character who likely plays a role in the unfolding events related to Paul and his nuclear experiment.

Robert Schenkkan takes on the role of a Government Aide, likely involved in handling the repercussions of the homemade atomic bomb situation.

Richard Council portrays another Government Aide, adding to the tension and complexities surrounding the secret nuclear project in the movie.

Fred Melamed appears as Howard, a character likely connected to the unfolding events and consequences of the high school student's atomic bomb project.