Law & Order: Criminal Intent (2001)

Season 1: Episode 2

When a museum curator and an art authenticator are found dead in what was set up to look like a murder-suicide, Goren and Eames follow the clues and realise that the deaths are linked to the sale of numerous art forgeries. Their investigation hits a dead end when they're unable to locate the forger until Goren seeks the help of another forger.