The Big Steal - Don Siegel, Lewis Allen

Jane and Duke (alias Capt. Blake) accidently meet in Vera Cruz while chasing flim-flam man Fiske. Soon the local Inspector General (El Gato) is involved. Fiske races across Mexico, pursued by Jane and Duke, trailed by the real Capt. Blake. The crafty Inspector General is waiting for them in Tihuacan but they all give him the slip, just in time for the climactic finale. Very tight script and pacing.