Lies Beneath Series by Anne Greenwood Brown

Calder White lives in the cold, clear waters of Lake Superior, the only brother in a family of murderous mermaids. To survive, Calder and his sisters prey on humans and absorb their positive energy. Usually, they select their victims at random, but this time around, the underwater clan chooses its target for a reason: revenge. They want to kill Jason Hancock, the man they blame for their mother's death.It's going to take a concerted effort to lure the aquaphobic Hancock onto the water... moreCalder White lives in the cold, clear waters of Lake Superior, the only brother in a family of murderous mermaids. To survive, Calder and his sisters prey on humans and absorb their positive energy. Usually, they select their victims at random, but this time around, the underwater clan chooses its target for a reason: revenge. They want to kill Jason Hancock, the man they blame for their mother's death.It's going to take a concerted effort to lure the aquaphobic Hancock onto the water. Calder's job is to gain Hancock's trust by getting close to his family. Relying on his irresistible good looks and charm, Calder sets out to seduce Hancock's daughter Lily. Easy enough, but Calder screws everything up by falling in love - just as Lily starts to suspect there's more to the monster-in-the-lake legends than she ever imagined, and just as the mermaids threaten to take matters into their own hands, forcing Calder to choose between them and the girl he loves.One thing's for sure: whatever Calder decides, the outcome won't be pretty. less

It's been thirty days, two hours, and seventeen minutes since Calder left Lily standing on the shores of Lake Superior. Not that she's counting. And when Calder does return, it's not quite the reunion Lily hoped for. Especially after she lets her father in on a huge secret: he, like Calder, is a merman. Obsessed with his new identity, Lily's dad monopolizes Calder's time as the two of them spend every day in the water, leaving Lily behind.Then dead bodies start washing ashore... moreIt's been thirty days, two hours, and seventeen minutes since Calder left Lily standing on the shores of Lake Superior. Not that she's counting. And when Calder does return, it's not quite the reunion Lily hoped for. Especially after she lets her father in on a huge secret: he, like Calder, is a merman. Obsessed with his new identity, Lily's dad monopolizes Calder's time as the two of them spend every day in the water, leaving Lily behind.Then dead bodies start washing ashore. Calder blames his mermaid sisters, but Lily fears her father has embraced the merman's natural need to kill. As the body count grows, everyone is pointing fingers. Lily doesn't know what to believe—only that whoever's responsible is sure to strike again. . . . less

Calder and Lily never imagined falling in love would mean breaking apart. But ever since Lily started wearing a glass pendant that once belonged to Nadia, Calder's adoptive mother, she's been having vivid dreams of what life was like for the mermaid matriarch. In fact, she's been dreaming as if she were Nadia! And Nadia, it seems, made a promise before her death. A promise to reunite Calder's biological mother with her son. Lily knows merfolk are bound to keep their promises... moreCalder and Lily never imagined falling in love would mean breaking apart. But ever since Lily started wearing a glass pendant that once belonged to Nadia, Calder's adoptive mother, she's been having vivid dreams of what life was like for the mermaid matriarch. In fact, she's been dreaming as if she were Nadia! And Nadia, it seems, made a promise before her death. A promise to reunite Calder's biological mother with her son. Lily knows merfolk are bound to keep their promises. Calder's not buying into it, though. He chalks up the dreams to stress. He wants Lily to focus on the future—their future, not the past. Which forces Lily to send Calder away. Calder goes, feeling rejected and more than a little tempted to revert to his hunting ways.  What both of them overlook is the present: Calder's sisters, Maris and Pavati, are fighting for control of the mermaid clan, and now that Lily and her dad have transformed into mer-creatures, both mermaids vie for daughter and father as allies. Which of the two mermaids can be trusted? Will Lily make costly mistakes, forcing her to descend to the depths of Lake Superior? And if Calder returns, will he be the same merman Lily grew to love? The stakes are high, with many lives at risk, but Calder and Lily must confront the past as well as their darkest impulses if they want a chance at being together. less