1967's "Secret of Blood" (Enigma de Muerte or Mystery of Death) was filmed in September, the last of John Carradine's Mexican quartet about six months before producer Luis Enrique Vergara's successful pursuit of Boris Karloff. Like "The Vampire Girls" this was another Mil Mascaras vehicle for director Federico Curiel, but the smallest role of all for Carradine, as always top billed yet on screen for a mere 12 minutes as Polito the Clown, leader of a meager carnival troupe consisting of clowns, a strongman, a knife throwing act, and a sharpshooter aiming at the target behind him using a handheld mirror. Mil Mascaras is called upon to guess the weight of a supremely hefty woman in the audience, otherwise free to conduct a little romance while investigating any nefarious activities centered around a coveted secret formula. Polito has a secret torture dungeon adorned with the Nazi swastika, with an electric chair, a handy whip, a mace, and a death ray that reduces its screaming victim to a bag of bones in mere seconds. Carradine introduces the picture while applying makeup before a mirror, not seen again for 20 minutes until he emerges in full clown regalia for an amusing bit of pantomime that makes one wish to see more. When out of makeup he's barking orders to subordinates in full Nazi military costume, a far cry from Reinhard Heydrich in 1943's "Hitler's Madman." A blonde Isela Vega makes her third appearance opposite Carradine, this time as the target in the knife throwing act, throwing herself at Mil Mascaras before proclaiming her love for the man with the blade (she appears in a single entry with Karloff, "Fear Chamber"). Our hero settles down at the circus after a single ringside bout, a bit too leisurely with much strolling and talking and very little action. John Carradine would return to Mexico on two more occasions, for director Juan Lopez-Moctezuma in 1974's "Mary, Mary, Bloody Mary," and Alfredo Zacharias in 1978's "The Bees."
