"Ivy Pocket arrives in London, protects the Clock Diamond, and realizes that her friend Rebecca may not be dead after all"--

"In Victorian London, Maisie Hitchins, a young detective who lives in her grandmother's boarding house, finds herself immersed in the excitement and glamour of the theater when she investigates the theft of a valuable necklace belonging to an actress friend of a longtime boarder." --

Iris's baby sister Rose breaks a necklace and then is discovered playing with Walter's missing harmonica.

When her precious pearl necklace goes missing, Pearl, who loves it as much as she loves singing, must retrace her steps, and with the help of resourceful and observant friends, finds her prized possession, which she securely fastens around her neck once again.

A twelve-year-old girl receives a birthday gift of a strange necklace that seems to make her invisible.

When Thea goes missing along with an ancient Mayan necklace, Geronimo Stilton is fast on the case, scouring Chichén Itzà for clues to find them.