The Silent Partner (1978 film)

The Silent Partner French title Largent de la banque is a 1978 Canadian heist film directed by Daryl Duke. It stars Elliott Gould, Christopher Plummer and Susannah York.

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 banks counters. He also figures out who the wouldbe 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 stickup note.Instead of informing his bosses or contacting the police, Miles devises a way of keeping the cash from most of his windows transactions in an old lunch box rather than in the banks till. As a result, when the Santa Claus robber holds up Miles at the tellers desk, he nets far less than the police and the bank think he has. ........

Source: Wikipedia