Mortar And Murder

Description for MORTAR AND MURDER by Jennie Bentley:

Avery Baker was once a New York textile designer, but inheriting her aunt's old Maine cottage has led her down a new career path -- home renovation. Finding a property's hidden potential has rewards and challenges -- especially when a mystery surfaces from behind the walls .. .

Avery and her boyfriend, Derek, are renovating a magnificent 225-year-old Colonial on Rowanberry Island, just off the coast of Maine. The DIY is going great even if the neighbor, a reclusive thriller writer, seems as strange and mysterious as his fiction. But his reputation seems in perfect keeping with what Derek and Avery discover next ...

The body of an unidentified woman with a piece of paper in her pocket bearing the address of Derek and Avery's Realtor is found floating in the sea near the island. Then a second woman is retrieved like jetsam from the harbor. But it's not until Avery discovers a secret room in the house, and learns about Rowanberry Island's long tradition of smuggling, that a bizarre link is made between the dead women -- and if it foretells anything, it's that things on the island are only going to get deadlier.

This is #4 in A Do-It-Yourself Mystery.