When his colleagues confirm that his acute leukemia-afflicated son Julio's (Agustín Martínez Solares, SANTO AND THE BLUE DEMON VS DRACULA AND THE WERWOLF's "el hombre lobo") days are numbered, Dr. Krallman (José Elías Moreno, Rene Cardona's SANTA CLAUS) comes to the realization that only gorilla's blood can kill the cancerous cells and his son will need a gorilla heart transplant to circulate the "more potent blood". With the assistance of faithful scarred Goyo (Carlos López Moctezuma, THE CURSE OF THE CRYING WOMAN), Krallman breaks into the local zoo and tranquilizes a gorilla. The heart transplant seems to be successful until Julio turns into an gorilla from the neck up and a fumbling sex maniac from on downwards and menaces the town. The authorities naturally believe the killings are the work of the escaped gorilla, but Lt. Arturo Martinez (Armando Silvestre, WRESTLING WOMEN VS. THE AZTEC MUMMY) - based on a survivor's description and a hybrid human/animal fingerprint - believes it to be the work of a "horrifying human beast" (hence the original Mexican title). A horrified Krallman tries to reverse the process with a human heart transplant using the purloined organ of comatose wrestler Elena (Noelia Noel, CARNIVAL OF CRIME); and it's a good thing Krallman later agreed with the hospital administration to hush up Elena's sudden disappearance from her hospital bed as Lt. Martinez's guilt-ridden wrestler fiancee Lucy [Norma Lazareno of Cardona's Andes cannibalism cash-in SURVIVE!] put her there in the first place with a cerebrum-puncturing skull fracture). The transplant returns Julio to his human form, but not for long if that red spotlight trained on Julio's sleeping face is any indication...

A remake of director Rene Cardona's own substantially tamer DOCTOR OF DOOM (1963) which pitted wrestling women against a brain-transplanting mad doctor and his apeman assistant, NIGHT OF THE BLOODY APES would have been lovably loopy in its original Mexican form as LA HORRIPILANTE BESTIA HUMANA, but Cardona added some continuity-breaking nudity - a woman who has her dress torn to shreds by Julio in one shot rushes into the next scene with the dress merely ripped at the shoulder - and open heart surgery footage for alternate adult version HORROR Y SEXO (Cardona's SANTO AND DRACULA'S TREASURE also had a rarer sexed-up color variant called EL VAMPIRE Y EL SEXO). One would think with Mexican exploitation's long trend of wrestlers (and wrestling women) against Dracula, Aztec mummies, and the like that NIGHT OF THE BLOODY APES would end in a showdown between Lucy - especially given her inability to keep her head in the game after gravely injuring Elena - and the gorilla man; however, Lucy and the other women in the cast are primarily cheesecake fodder (then again, the police are no more effectual). When the film arrived in the states, exploitation producer/director Jerald Intrator - whose distribution company started out with reissues of M and SHOOT THE PIANO PLAYER in the mid sixties - added explicit eye- gouging, head-ripping, throat-tearing, head-scalping, face-smashing, chest-stabbing gore inserts (and some additional nudity with a lighter-skinned body double for the first victim) to create what is widely known as NIGHT OF THE BLOODY APES. The literally-translated English dub track also sports such highly quotable lines like "I'll say that's absurd, the proofs are circumstantial, it's more probable that of late more and more you've been watching on your television many of those pictures of terror", which is even funnier since that line is in response to a hypothesis prefaced with "What I'm going to say might sound absurd..."