Even if you recently reread The Hobbit, you might leave the theater confused about some of the characters—and subplots—you just witnessed.

Spencer Patterson dug through the book and sought help from various online Tolkien sites, so you won’t have to.

Azog, the Pale Orc The main antagonist in An Unexpected Journey only gets name-checked in the novel, by way of setup in the opening chapter (“Your grandfather Thror was killed, you remember, in the mines of Moria by Azog the Goblin,” Gandalf says to Thorin) and in a footnote toward the end of the book. Since the dragon Smaug barely shows up in the first film, beefing up Azog’s screen time makes some sense, though his plotline feels rather shoehorned in. As for why he’s gone from goblin to orc—or is now known as “The Desecrator”—you’ll have to wait for Peter Jackson to weigh in.

Radagast the Brown Blink and you might miss Gandalf’s wizard cousin in the novel. He’s mentioned once, during a conversation between Gandalf and Beorn, the latter a character not yet introduced in film. Radagast actually sees more page time in The Lord of the Rings and supplemental readings The Silmarillion and Unfinished Tales, but in the first big-screen installment of The Hobbit, the brown wizard makes a fairly lengthy appearance, eating magical mushrooms, riding around the forest on a sled drawn by rabbits and coming face to face with …

The Necromancer This extreme evildoer (perhaps most famous as the title of an early Rush song) does his thing off-page in the novel, referenced only during the first and last chapters by Gandalf, who goes off to deal with him about halfway through the story. The Necromancer has already made a far greater impact on the films, and it’s a safe bet his showdown with Gandalf will be a centerpiece of the remaining story. And to those looking for links between The Hobbit and The Lord of the Rings beyond Bilbo, Gandalf, Gollum and the ring, deep Web research reveals there are those who believe The Necromancer is actually some form of—shudder—Sauron himself.