I would have been. It's not that Nicholson is at all a bad actor, but I have a hard time imagining him outside of modern settings. To me, Jack Nicholson belongs in gritty, urban dramas the way a fish belongs in water. Still, early in his career Nicholson worked as a jack-of-all-trades for Roger Corman, who had Nicholson working as a writer and a director in addition to acting in all sorts of stuff he eventually became too good for.
So, The Terror casts Nicholson as Lt. Andre Duvalier, a French solider who has become separated from the rest of his company. On the beach, he encounters a beautiful woman who does not speak, but disappears into the sea. Duvalier tries to follow, but is attacked by a giant bird. He passes out and awakens in the home of an elderly peasant woman, who tells him that she has not seen the woman he seeks. She is obviously lying.
Duvalier makes his way to the castle of Baron Von Leppe (Boris Karloff) who initially tries to turn him away, but eventually gives in to his persistence. Von Leppe has a painting of the girl, and Duvalier eventually pieces together a 20-year-old story of betrayal and murder involving identity theft, revenge, and a ghost. That Guy Dick Miller plays something other than a salesman (for once), and Jonathan Haze (Seymour from the original version of The Little Shop of Horrors) is seen, but not heard.
I'm sorry, I really can't give you more than that, because I don't want to spoil anything. The Terror is a very weird movie. I don't mean to imply that there's great brilliance wrapped inside this ugly and wildly uneven package, but it's worth a look.
We use the term "exploitation" to refer to a certain type of filmmaking, but I'm not sure that most people really understand where it comes from. Sure, these movies tend to exploit their actors and their audience, but the term really refers to getting the best film you can out of limited resources. Roger Corman was a master at this, and legend has it that when he finished shooting his film The Raven, he found himself with a couple of days left on Boris Karloff's contract. He commissioned the barest outline of a story, and got as much work out of Nicholson and Karloff as he could. The story then congealed around those scenes, and was made using the leftover sets from Corman's other recent pictures. Directing duties were passed between Corman, Nicholson, exploitation filmmakers Monte Hellman and Jack Hill, and a little-known, talentless nobody called Francis Ford Coppola, whom you've probably never heard of.
Given all of this, the end result should have been an unwatchable mess, but it turns out to be quite palatable, and in fact, the convolutions of its plot are clumsy, but appear to be complex. It should just fall apart on the runway, but instead it flies (and attacks Duvalier until he passes out).
Shifting gears a bit, I wanted to touch briefly on the subject of accents. Jack Nicholson sounds exactly as he always does, and doesn't even try to affect a French accent. The same goes for veteran Corman conspirators Dick Miller and Jonathan Haze. Boris Karloff, on the other hand, does his usual plummy British. Is it better, in a movie like this, to try to fake regional accents to the annoyance of international viewers, or is it better to let everyone sound like themselves? Or is it better just to say "to hell with it" and make them all British? I don't know that there's a right answer to that question, but trying to imagine Jack Nicholson with a French accent makes my head hurt.
You can watch the movie in its entirety on YouTube: