This obscure Spanish movie is listed in my trusty Aurum Encyclopaedia of Horror, but barring a ghost or two (friendly) and a few old, dark house tropes (hidden passageways and secret doors), there isn't much to qualify it as such. It's more of a fantastical mystery with comedic elements: the spirit of Don Robinson de Mantua (Félix de Pomés), who is believed to have committed suicide, tells Basilio Beltrán (Antonio Casal) that he was in fact murdered. The spook asks the young man to protect his niece Inés (Isabel de Pomés), who he says is in danger from the man who killed him, a criminal mastermind who commands a gang of hunchbacks. When Inés goes missing, Basilio tries to find her, his search leading to a subterranean city deep beneath the streets of Madrid.
The Tower of the Seven Hunchbacks is something of an oddity: although made in 1944, it looks and feels like something from much earlier, its bizarre, seemingly-random plot possessing the dreamlike quality of a silent movie; the direction and acting also have that silent era quality, with the cast giving somewhat exaggerated performances, while the production design wouldn't look out of place in a German expressionist picture of the '20s or an early Universal horror (the spiral stairs leading down to the underground city being the most impressive shot). The film starts off with a jaunty musical number in a nightclub, adds humour with a scene in which de Mantua helps Basilio to win at roulette, gets really daft with the introduction of Napolean's ghost, and turns into a mystery with Inés abduction. The finalé adds suspense to the mix, as Basilio navigates a network of tunnels, locates the hidden city that is home to the hunchbacks, and attempts to escape with Inés.
It's all a bit too scattershot in tone and narrative for me to call it a great film (I'm still unsure as to why the villains are all hunch-backed), but it's also this randomness that makes it a fun watch.