Festergrimm

"When their nemesis returns with plans to reopen the waxworks museum, Herbie and Violet suspect nefarious motives as they are led into the dark Netherways below the town and into the tragic past of a famous toymaker/inventor whose story holds the key to Eerie-on-Sea's deepest secret"--
When Sebastian Eels turns up in Eerie-on-Sea, seemingly back from the dead, it can only spell bad news. The town may welcome his entrepreneurial scheme to resurrect Festergrimm's Waxworks, a dusty and defunct old gallery of spooky characters from Eerie legend, but Herbie and Violet are suspicious of his motives. And when they learn the legend of Ludo Festergrimm the clockmaker, creator of a vast mechanical robot that wrought havoc in the wrong hands, they know they are on the right track. But how can they get the residents of Eerie-on-Sea to believe them? -- adapted from jacket.