SOS Help remember the name of the movie

The plot is approximately as follows: a lawyer or a specialist in solving any dubious cases, is talking with a guy involved in a crime - either the murder of a girl, or disappearance. Almost the entire film takes place in one room. And I remember the ending of the film: he looks out the window opposite, and there the woman takes off her mask (makeup and wig) and it turns out that this is the mother of the murdered woman and she was having a conversation with the criminal. I really want to see this film again.