AllMovie

The screenplay for Warner Bros.' Black Diamond Express was credited to "Mark Canfield," one of the many pseudonyms of Warner workhorse Darryl F. Zanuck. Monte Blue heads the cast as a muscular railroad worker, in love with heroine Edna Murphy. Several obstacles are placed in the path of true happiness for Blue and Murphy, not least of which is a train holdup in which the hero's boss is killed. Taking on the villains single-handedly, Blue ends up struggling to bring a runaway Pullman car under control, as the car and its passengers careen down a steep slope. Critics who enjoyed Monte Blue but were unhappy with his choice of vehicles were gratified to find this screen stalwart back in the sort of action fare he did best.