When the twins find out that Mayor Knightleigh has continued his plans to build the hotel, using Smelterburg work crew. Unexpectedly, someone called 'The Mason' sabotages the work crew using the twins own prank plans. The twins come across a laboratory and a Balm-like mixture which they presume belongs to 'The Mason'. It turns out the former head of local building company Smithy & Sons, Eugenia Smithy, was fired from the company for losing the job. It turns out that Eugenia wanted to get the Smelterburg company kicked out so Smithy & Sons could get the job. The twins soon blackmail Eugenia into helping them sabotage the construction. In return she gets her job. Unfortunately, thanks to Eugenia, the twins' efforts backfire and the hotel work proceeds. It is discovered that the lab was not Eugenia's, leaving the identity of the lab's owner a mystery. The story ends with one of the seedlings of Ellen's plant 'Berenice' (which was destroyed by Stephanie Knightleigh) grows in a balm covered beaker from the lab.