Have your parents ever gone on vacation without you?!? In Lulu’s Mysterious Mission, Lulu’s parents have decided to leave her home with “the best babysitter in town—maybe the world—,” Ms. Sonia Sofia Solinksy. Lulu doesn’t agree with any of this, so she comes up with several plans to try to get rid of the stern babysitter. Nothing seems to work, and it’s not until Lulu tries to blackmail Ms. Solinsky that she learns this trained professional babysitter is also a retired spy—code name Triple S—and Lulu’s dream is to be a spy when she grows up. Luckily for her, Triple S agrees to teach Lulu tricks of the trade as long as Lulu is obedient and keeps the spy training a secret. Can Lulu follow through with the deal? And what will happen when her parents finally return from their vacation?