The Widow's Light. The Greyhaven Murder Files, #3

A ship that sank thirty years ago has returned to Greyhaven. Lighthouse keeper Gideon Quill is the only person who sees it-a vessel moving through dangerous winter waters without navigation lights or a signal on radar. By morning, Gideon is dead inside the locked lighthouse tower. The evidence points to suicide. His widow knows better. As a violent storm cuts Blackglass Island off from the mainland, Mara Wren discovers coded messages hidden in decades of lighthouse logs.
The entries identify the dark vessel as the Saint Aveline, a cargo ship officially lost with all hands thirty years earlier. With the electricity failing and every suspect trapped on the island, Mara and Detective Inspector Rowan Vale uncover secret salvage operations, falsified maritime records, and a family fortune built on disaster. But the closer they come to identifying Gideon's killer, the nearer the lighthouse comes to going dark for good.
Outside, something large is moving through the storm. And a ship that does not legally exist is coming back for the evidence.