Where Did You Get This? (1952)

A young medical student and his valet help a professor invent a serum that renders living beings invisible. They decide to test the serum on the dog of an elite family, that has been brought in for treatment - and it works. When returning the dog, the student meets the owner, the beautiful Salwa, and they fall in love. He asks for her hand in marriage, but she tells him hat her father has already chosen another husband for her, an obnoxious rich casino owner. Salwa fakes illness so she and the student can be together, but the casino owner and his lackeys find out about their affair and accuse him of trying to kidnap Salwa. However, the student realises that the casino owner also runs a drug cartel, and using the invisibility serum he exposes them, and wins the acceptance of the father.