So, here's a Spanish language comic book and have no idea what it's about. Alan Duff is evidently some kind of tough guy, maybe a private detective because he dodges a knife and punches a guy -- both de rigueur actions for a private eye.
Alan Duff was written and drawn by Julio Vivas (born Julio Vivas Garcia in 1923). Vivas created the Alan Duff comic for Editorio Marco in 1952. The web site Comic Book Plus has 30 of the Alan Duff adventures available. I don't know if there are any others. In fact, I can find very little about Alan Duff on the internet (except for the fact that his name is shared by a New Zealand author) and very little information about Julio Vivas (except that he shares a name with a baseball player and with an actor).
The joy of foreign language comic books is that you can make up your own stories to go with the pictures. I do the same thing with the telenovelas on Spanish Language television.
Anyway, here's "El Vampiro." (Should I mention that I didn't see anything resembling a vampire in the artwork? No, I think not.) If you happen to read Spanish, you're in luck. If you happen to have a Spanish language dictionary, you're also in luck. If you choose to make up your own story with the pictures, let me know; I'd be very interested in what you come up with.