Capt. Mephisto: Remember, any attempt to discover which one of the owners is my true personality will result in your immediate destruction!

- Roy Barcroft in Manhunt of Mystery Island

Capt. Mephisto: You wouldn't dare trick me?
Prof. William Forrest: Trick you? I'd kill you if I thought I could escape afterwards! As it is, I'm obeying orders.
Capt. Mephisto: Don't tax my patience too far!

- Roy Barcroft in Manhunt of Mystery Island

Sidney Brand: I've often wondered how you change from one person into another.
Capt. Mephisto: No doubt you have. I'll tell you this much. The appearance of human beings' stature, complexion and pigmentation is controlled by the molecular arrangement of the blood corpuscles. I have found a means of altering that arrangment.
Sidney Brand: I understand.
Capt. Mephisto: If I thought you really did, I'd *kill* you!

- Roy Barcroft in Manhunt of Mystery Island