2. Moment of Rupture ... these happy moments end tragically and violently before the start of the story. Something happens, whether external to the characters or through the characters' own actions, that causes the idyllic past to end.

At the start of a Noir story, characters are doing their best to cope with the trauma of losing their happy pasts... but usually in unhealthy ways: they're indulging in vices like gambling or drinking in an effort to dull their pain. But nothing they do make them forget what they lost.