Festergrimm / Thomas Taylor ; illustrated by Tom Booth.

Enhanced descriptions from Syndetics:

In the fourth tale in this beloved series, villainous Sebastian Eels returns to Eerie-on-Sea, thrusting Herbie and Violet into a new adventure involving a missing girl, a spooky wax museum, and a dangerous clockwork robot.

Herbie Lemon, Lost-and-Founder at the Grand Nautilus Hotel, and his fearless friend Violet Parma have unearthed many secrets in their village of Eerie-on-Sea: secrets lurking beneath the waves, lapping onto the beaches, and lying behind locked doors. When their brilliant and ruthless nemesis, Sebastian Eels, returns with a plan to open the long-shuttered waxworks museum, Herbie and Violet suspect nefarious motives. Their investigation leads them into the dark Netherways below the town--and into the tragic past of the famous toymaker and inventor Ludovic Festergrimm and his doomed daughter, Pandora. Sebastian Eels is convinced that within the story of Festergrimm is the key to Eerie's deepest secret--a secret in which Herbie himself plays a crucial part--and he'll stop at nothing to uncover it, including bringing a terrifying clockwork legend back to life. With echoes of fairy tales and monster movies, plus a dismembered finger or two, this is a deliciously creepy addition to a fantastical mystery series that is perfectly calibrated to thrill middle-grade readers.