Doctor Strange teams up with a mysterious teenage girl from his dreams who can travel across multiverses, to battle multiple threats, including other-universe versions of himself, which threaten to wipe out millions across the multiverse.  They seek help from Wanda the Scarlet Witch, Wong and others.
 
This is as close to the horror movie genre Marvel has ever gotten.  A few more "Raimi" scenes and this one could've been rated R.  
 
FUN FACT:  Director Sam Raimi previously added two references to the character Doctor Strange in Spider-Man 2 (2004):
 
Joe's Pizza (where Peter Parker is working at the beginning) and the billboard showing Mary Jane are located on Bleecker Street (where Doctor Strange's Sanctum Santorum is located).
The name of Doctor Strange is suggested to J. Jonah Jameson as a possible name for Dr. Octavius, to which Jameson replies: "But it's taken!"