The past couple of years have been quite the up and down ride for Eddie Redmayne. The English actor won Oscar gold for hardly moving in “The Theory of Everything,” was nominated again for wearing his emotions on his stylish sleeves in “The Danish Girl,” and was reviled for shifting between shouting and whispering in “Jupiter Ascending.” In “Fantastic Beasts and Where to Find Them,” Redmayne makes terrific use of his inquisitive eyes, shows just the right amount of mischievousness, and wonderfully wields a wand as Newt Scamander, a British wizard and writer who has come to America in the 1920s with his magical briefcase to do research for his next book, which happens to be the same title as the film. With a script by J.K. Rowling that’s based on the slim and plot-free “textbook” she wrote as an offbeat offering to her Harry Potter fans, the film traces Newt’s New York adventures and his relationships with other wizards, with good and bad muggles and, of course, with lots of those creatures. Redmayne, 34, spoke about the film last week in New York.

Q: How did the part initially come to you?

A: I got a call saying David Yates (who directed the last four “Potter” installments) wanted to meet with me. But I wasn’t allowed to know what it was about. I was in London, and he’s a member of a club there called Blacks. Down in the basement was David Yates, sitting next to a little fire. Now I’ve had this Globe-Trotter case for a long time. I keep my work stuff in it. I sat down next to David at the fire, and he told me J.K. Rowling was writing a script. He started telling me the story, about Newt and what his characteristics were, and that he had this case. Then I noticed my case on the floor, and I gently started pushing it back under table so I didn’t look like one of those actors that turned up (at an audition) dressed as Superman or whoever they were going to play.

Q: Had you known anything about the book or the script?

A: No, but the story he told was deeply intoxicating, and then after the first couple of chapters he stopped. Then I would come back every month or two, and he would tell me the next few chapters. Eventually I got to read the script, and I was primed for it. I loved that there was a thriller element, a sort of darkness to it, a comedic element, and the romances, and of course, heart, which the Potter films always had. But I still hadn’t been offered the part (laughs). When I came back for another meeting with David I thought, maybe this was when I should have brought my case. But he offered me the part in that meeting.

Q: The Potter characters are very familiar. But we’re seeing these characters for the first time. Did you get to put a lot of your ideas into them?

A: The characters were so well drawn in the script that you really got a sense of who they were. But I have a really bad imagination, and I knew we were going to be doing a lot of CGI work. So I asked David if he could involve (the actors) in all of the process. So I got to go and look at the locations and to see the pre-viz work and to talk to the guys who were animating the creatures.

Q: Did you have any contact with J.K. Rowling about it?

A: She had written this glossary for comic relief, and it didn’t say much about who Newt was. When I read the script, not only was the dialogue wonderful, but the detail in J.K.’s script was so intricate and enticing, it was all there. I had an absolute sense of who Newt was from the first time I read it. And when I met with her about a week before we started filming, she talked about where Newt came from in her imagination. That conversation was amazing, and kind of kick-started me in the right direction.

Q: It’s a gigantic, visual effects-filled movie. Was there one part that was a big challenge for you?

A: I guess it was the scene in which Newt first goes down into his magic case with Jacob Kowalski (played by Dan Fogler), and lots of the creatures were there. I felt that if you didn’t believe in Newt’s relationship with the creatures, the film would kind of fall in on itself. Because it’s a scene in which the audience and Jacob get introduced to all these different creatures, I wanted you to believe that Newt had different relationships with different creatures. But some of them were played by puppeteers, and some of them, because they were CGI, weren’t even there. It was quite a technical scene, but all I cared about was that the audience would get the emotional relationships.

“Fantastic Beasts and Where to Find Them” opens on Nov. 18.

— Ed Symkus covers movies for More Content Now.