Echoes at Midnight. Echoes in the North Country, #2

Told in alternating timelines, this romance novel with a murder mystery twist takes place on the 16-acre island of Garden Key, the second largest island of the Dry Tortugas, a group of sandbars 68 miles southeast of Key West in the Gulf of Mexico. It's home to Fort Jefferson's hexagonal fortress. Beyond the moat, where you'll find on two sides the docks, primitive camping grounds on the southern part of the island, picnic areas under swaying palms, and immaculate white sand beaches.
This is where darkness descends, and then murder and madness ensue. While their group starts with more than a dozen people in adjacent campsites, mostly couples seeking a romantic night camping are suddenly thrown together with the challenge of escaping a serial killer far away from civilization. Callie, a young architect and fiancée, appreciates the islands' beauty and danger early on, as do veterinarian Oliver, electrical engineer Jack, and restoration architect Liam.
While everything starts happily, there are dangers and surprises that nobody could have foreseen. Will they learn to trust each other, or will their interpersonal obstacles be more devastating than the impossible physical and emotional challenges of escaping an unknown murderer who could be any one of them? The majority of the group is reluctant to team up with the one mentally challenged man, Jack, because of the whispers of suspicion surrounding his ex-wife's untimely death that they all were made aware of by his buddy Oliver on the two-and-a-half-hour ferry ride to the islands earlier in the day.
But the closer Callie gets to Jack, the more she questions his innocence. However, a series of strange occurrences at the camping site makes Callie fear she might be the next to disappear in this romantic suspense thriller.