On March 12, 1944 in Avalon Bay, during World War II, a woman named Rosemary Chatham writes a letter to her boyfriend, breaking up with him. On June 28, 1945, Rosemary is attending a graduation dance with her new boyfriend Roy. The couple leave the dance to a lakeside gazebo. There, they are attacked by a mysterious prowler wearing an army combat uniform, who impales them both with a pitchfork and leaves behind a red rose. On June 28, 1980, college senior Pam MacDonald is making last-minute arrangements for that night's graduation ball, the first to be held since the 1945 murders.