Morteza, in his fifties and just out of jail, is suspected of being involved in the death of a drowned child. Taher, the police officer in charge of his case, first believes Morteza is guilty, like everybody else does, but then finds out that he knows Morteza. The two men's relationship goes back 30 years, with its roots lying under the cold waters of the lake... Soon convinced by Morteza's innocence, Taher decides to prove it despite everything.