Anticipation for “Fantastic Beasts and Where to Find Them” has been so high that fans began dressing up as its main character, Newt Scamander, based solely on the trailer. That surprised its star, Eddie Redmayne, when he attended Comic-Con International in July and looked out into the audience only to see several Newts staring back at him.

“I found that deeply exciting and weirdly shocking,” he said by phone from London. Imagine what will happen when the movie arrives Nov. 18, and eager Harry Potter fans get another look at J. K. Rowling’s wizarding world.

Ms. Rowling’s story — this is her debut as a screenwriter — follows a self-proclaimed “magizoologist” who was expelled from Hogwarts but eventually wrote one of the school’s most important textbooks. He has been traveling the world collecting, studying and building relationships with all kinds of magical beasts, toting them in a suitcase as part of his mission to educate wizards about why beasts are so important to them. But when some creatures escape and take to the streets of 1926 New York, the mishap could expose the wizarding world and lead to war.

While the beasts are at the heart of the film’s title, humans are at the heart of its story, said David Heyman, a producer on the “Harry Potter” movies: “The ‘Potter’ films and this film all emanate from a place of character. Newt is an outsider, a bit like all of [J. K.’s] characters.” That’s why he feels best able to connect with the beasts, though eventually he connects with people as well.