Murder in the Lighthouse by Vickie McKeehan

Juggling personal issues like discovering a newfound sibling and questions about her DNA results—Lucien Sutter and Brogan Cole—seem forever destined to take on the hard-to-crack cases. Thrown into a disappearance that turns into a complex murder investigation, they need to learn how Sam Heywood ended up dead inside a locked lighthouse and if his senseless murder is connected to his sister’s disappearance just three weeks earlier. Of course, the two cases are connected. But proving it to skeptical law enforcement becomes almost an insurmountable task. As they navigate through a maze of cynics and roadblocks, they uncover a shocking connection to a serial killer from 1999. But will anyone believe them before their suspect continues adding to his victim count?