Attack of the Jack!

Attack of the Jack is the second book in Goosebumps SlappyWorld.

Plot
Devin and his sister Violet are visiting their Uncle Jack for the summer. He lives in an old house by the seashore. Jack was a sailor and he has collected strange and fascinating items from the sea. While exploring a back room, Devin and Violet discover a locked trunk, which is a pirate's chest. The trunk is wrapped in old, heavy chains and is also locked with a huge rusted lock. But Devin and Violet managed to get it open.

They lift the lid slowly and see that's filled with antique jack-in-the-boxes. One box is hidden under the others, covered in dust and it plays an odd, unpleasant song. Then up pops a mean-looking puppet, an old pirate with a dirty red bandana over his long greasy hair, scars on his cheeks, a beard and one eye missing. Then he bounces on his spring, rasping "Thanks for letting Sailor Jack out!". Devin and Violet now face new and troubling questions: Will Jack return them to their uncle? Just how much is a pirate's promise worth?