The film was the first to be produced by Carolco Pictures and one of the earliest films from Canada to take advantage of the Canadian government's "Capital Cost Allowance" plans. The Silent Partner is also notable for being one of the very few films to have a score composed by Oscar Peterson, and for featuring an early big-screen appearance by John Candy.
Miles Cullen (Elliott Gould), a bored teller at a small bank in a large Toronto shopping mall (the Eaton Centre), accidentally learns that his place of business is about to be robbed when he finds a discarded note on one of the bank's counters. He also figures out who the would-be robber will be when he sees a mall Santa Claus hanging around outside the bank whose "give to charity" sign is in handwriting similar to that on the discarded stick-up note.
Instead of informing his bosses or contacting the police, Miles devises a way of keeping the cash from most of his window's transactions in an old lunch box rather than in the bank's till. As a result, when the Santa Claus robber holds up Miles at the teller's desk, he nets far less than the police and the bank think he has.
The Santa Claus thief, a misogynistic psychopath named Harry Reikle (Christopher Plummer), figures out what happened, then makes a series of desperate and violent attempts to get the money (totaling CA$48,300) that Miles has kept for himself. Reikle starts following Miles to and from his home, making harassing phone calls.
Miles's coolness under pressure attracts the attention of bank colleague Julie Carver (Susannah York), who has been having an affair with the bank's married manager Charles Packard (Michael Kirby). After escorting Julie to a Christmas party at the Packards' house, he reveals his own attraction to Julie. Their co-worker Simonson (John Candy) becomes infatuated with a young ditzy blonde named Louise (Gail Dahms), a teller at the bank. Miles discovers that Louise is cheating on Simonson with another co-worker, but never reveals what he knows, even after Simonson and the pregnant Louise get married.
When the menacing Reikle breaks into Miles' apartment and trashes it to look for the stolen bank money, Miles turns the tables yet again by following Reikle, then sets him up to be arrested for the theft of a delivery truck. When brought to the police station to identify Reikle in a lineup, Miles does not point him out, aware that Reikle would then implicate him in the bank robbery.
A few months later, at his father's funeral, Miles meets a flirtatious woman named Elaine (Celine Lomez), who says she was a nurse who had been caring for his father. In fact, Elaine is secretly working with Reikle, who is still in jail. Elaine has been visiting Reikle there. But by the time Elaine discovers that Miles has stashed the holdup money in a safety deposit box at the bank, Reikle no longer trusts her, correctly sensing that Elaine has become romantically involved with Miles.
Miles figures out that Elaine is not who she claims to be. But when he loses the safety deposit key to the box where he has stashed the stolen bank cash. Miles gets Elaine to help by disguising herself as a customer, needing a copy of the safe deposit keys made in order to remove the money from the bank. Julie, meanwhile, has begun to suspect something about Miles and his new girlfriend.
Reikle is released from jail and confronts Elaine over where her loyalties lie. When she admits that she has indeed fallen in love with Miles, an enraged Reikle murders and decapitates her at Miles' apartment. Miles is forced to dispose of her body in the foundation for the bank's new building, under construction. Reikle then confronts Miles and says that he intends to kill him, too, unless he gets the money. Miles refuses to part with it except in a public place where no harm can come to him.
They agree that Reikle will come to the bank, again in disguise, and be handed the money at Miles' window, where Miles will feel safe. The next day, Reikle arrives dressed as a woman. Once he is paid the money, he promises to kill Miles anyway for the inconvenience that he's been caused. Anticipating that Reikle would say just that, Miles immediately presses an alarm button. Reikle pulls a gun and shoots Miles, then flees into the mall, where he is shot dead by a bank security guard.
A wounded Miles is taken away by an ambulance. Julie goes along, telling Miles that she has figured out everything. He reveals to Julie that he still has the stolen bank money and that he only gave Reikle again a few thousand dollars of the bank's money from the till. Both decide that the time might be right to quit their jobs and find some other line of work.Elliott Gould - Miles Cullen
Christopher Plummer - Harry Reikle
Susannah York - Julie Carver
Celine Lomez - Elaine
Michael Kirby - Charles Packard
Ken Pogue - Detective Willard
John Candy - Simonson
Sean Sullivan - Frank the Security Guard
Gail Dahms - Louise
Michael Donaghue - Berg
John Kerr - Detective No. 3
The Silent Partner did well in Canada both critically and financially, winning several Canadian Film Academy Awards including Best Picture and Best Director. The film was a sleeper upon its US release, with Brendon Hanley of the film database Allmovie noting that the film"...stands out as one of the best sleepers of the late '70s".
Roger Ebert, in his March 30, 1979 review in the Chicago Sun-Times, awarded three-and-a-half of a possible four stars to the film, calling it "a thriller that is not only intelligently and well acted and very scary, but also has the most audaciously clockwork plot I've seen in a long time." Ebert described it as "worthy of Hitchcock."