Robert B. Parker's Bull River by Robert Knott

Robert B. Parker's Bull River (A Cole and Hitch Novel) - Virgil Cole and Everett Hitch apprehend Alejandro Vasquez and bring him to San Cristóbal to stand trial.  While they are there, a local bank is robbed.by the president of the bank, Henry Strode.  Strode and his wife, Catherine, disappear.  However, Strode is later found, beaten and left for dead, on the porch of a local whorehouse.  Cole and Hitch find themselves looking for the robbers and kidnappers.  Meanwhile, Vasquez, tells Cole and Hitch that he knows the robbers and where they are going, but will only exchange the information for a deal, and that the only way to get to the place is to personally show them the way.