The Triangle:

Grim-faced café owner Rick Blaine (Humphrey Bogart), sultry ex Ilsa Lund (Ingrid Bergman) and her husband, anti-Nazi insurgent Victor Laszlo (Paul Henreid).

Does It Get Complicated?

Nazis are involved.  Nazis always complicate things.

But here Ilsa is the biggest problem.  Imagine your ex rocking up with another lover on their arm, and asking you to risk life and limb to help them?  Leaving aside the war, that’s just shitty behaviour.

No wonder Rick can’t decide whether to do as she asks or shop Laszlo to the Nazis.