And there it is. Mere minutes in, Kaecilius has already fucked up his mission in two ridiculous ways that will dictate the rest of the plot. At this point the Ancient One, played by an alarmingly bald Tilda Swinton, shows up to instigate a fabulous M.C. Escher chase scene so elaborate and creative that it likely distracted you from the fact that the film's villain probably shits crayons.
Wait, What Was Their Plan Again?
The stolen pages, we find out later, contained a ritual to awaken an ancient evil named Dormammu. The rest of the movie revolves around hunting Kaecilius down and thwarting his plan to use Dormammu's power to create an immortal (albeit hellish) existence for all of humanity. Seems straightforward, as villain schemes go.
Doctor Strange, meanwhile, begins his Hero's Journey at the temple, and in an oddly clumsy scene, he happens to be strolling around the Masters Only section of the library, where he grabs a totally random book off the rack. He then casually flips it open to see that pages are missing. That's right: Of all of the hundreds of books in the library, he happens to grab the exact one that's key to the entire plot. They couldn't have had it off in its own special case or something, so there'd be a reason for it to draw his attention? Whatever, it doesn't matter.
Strange is informed by the grumpy librarian that the book is a series of spells that can manipulate time. The librarian then tells Strange that he'll murder anyone -- including Strange -- who attempts to steal one of the sacred books on his watch. But that is no match for the plucky doctor! Strange is intrigued, and learns just enough magic to open mini-portals to steal three forbidden books right behind the librarian's back! It's an adorable bit of magical slapstick ...