Season of Fear (1989)

Fred Drummond (Ray Wise) longs to reconnect with his adult son, Mick (Michael Bowen). Fred hasn't been part of Mick's life for two decades. In the meantime, he has married Sarah (Clara Wren), a gorgeous woman many years his junior. The reunion seems to go well -- until Mick and Sarah begin a tumultuous affair. If the bizarre love triangle between father, son and stepmother weren't dangerous enough, it soon gives life to a conspiracy that's even more complicated and deadly.