It's a convoluted plot, no matter what you do, but here's what AFI starts with:
"As he is about to sail from Veracruz, Mexico, Duke Halliday is confronted at gunpoint by Capt. Vincent Blake. While Blake is searching Duke's luggage, however, Duke knocks him out and steals his identification papers. Duke then shoves his way through a crowd and is chastised for his rude behavior by disembarking American Joan Graham. Leaving Duke at the pier, Joan finds Jim Fiske, her double-crossing fiancé, in a hotel room and demands that he return the $2,000 he "borrowed" from her. The smooth-talking Fiske promises to return the money as soon as he makes a paid delivery, but while Joan is taking a shower, he slips out with the valuables. Duke then walks into the room looking for Fiske and identifies himself to Joan as Capt. Blake. Feigning nonchalance, Joan dismisses Duke, but then finds Fiske in the hotel garage and tells him about Duke's visit. Just then, Duke appears and begins fighting with Fiske. Fiske gets away, and Duke and Joan are brought to the local police station. Once again Duke identifies himself as Blake and tells Inspector-General Ortega that he is pursuing a fugitive. The amiable Ortega allows Duke and Joan to go their separate ways, but immediately orders a tail put on them."
There was a definite character that Robert Mitchum played for the most part. Jeff Bailey from OUT OF THE PAST and Harry Powell from NIGHT OF THE HUNTER were more exception than rule. Typically, as in this film, Mitchum was the good guy in the bad world. We are introduced to Mitchum in this film without a character name, beating on a guy who shows a badge. Thrust as we are in the middle of this mess, Mitchum is a criminal, on the run and resisting arrest. As the film unfolds, we find out the real situation and the real criminals are revealed. But, until that point, we've got pretty effective (and in the hands of director Don Siegel) quickly-paced noir. It also features a re-teaming of Mitchum with his OUT OF THE PAST femme fatale, Jane Greer. I recommend it, and you can find it in the Warner Bros. 4th DVD Film Noir set.