Is Area 51's cover blown?! Sky and her otherworldly friends scramble to protect its secrets when a UFO goes missing in the fourth installment of this laugh-out-loud, Edgar Award-nominated series for young readers.

For the first time since Sky got to Area 51, things seem to be under control. No bunker hideouts. No incoming space toilets. No kidnappings of beloved relatives. In fact, everyone is in a celebratory mood because a special government visitor is coming to Area 51!

But on the morning of the visit, a UFO goes missing from the science lab. And then a mysterious whistleblower goes to the media saying they have evidence of a UFO landing! Did someone steal the UFO in order to reveal it to the whole wide world? Sky and her friends have less than a week to solve the mystery of the missing UFO, or all of Area 51's secrets will be at risk. Guess things aren't so calm after all!