This cover image released by William Morrow shows "Under a Dark Sky," by Lori Rader-Day. (William Morrow via AP)

(AP) — ‘A dark sky park where even the slightest glimmer of light is blocked out provides a fascinating backdrop for Lori Rader-Day’s inventive fourth novel. The darkness that permeates the park’s environs also works as an imaginative metaphor for murky emotions and concealing secrets, even from those to whom one is closest. A shrewd plot and realistic characters also soar in “Under a Dark Sky.”

Mired in grief since her husband, Bix, died nine months ago, Eden Wallace decides to keep a reservation at Straits Point International Dark Sky Park in Michigan. Before he died, Bix planned the park visit as a surprise for their 10th-wedding anniversary, and she has just found the reservation while cleaning out a drawer. It’s an unusual gift because Eden’s fear of the dark is pathological, but she hopes the visit will give her a new perspective on her life, and get her away from her Chicago home.

But instead of solitude, Eden is sharing the resort with six strangers — college friends who booked the cottage for a reunion. Her immediate reaction is to leave, but Eden has been doing a lot of hiding lately, avoiding people and alienating friends who are tired of hearing about Bix’s death. Besides, the park will not refund Bix’s payment. Although the friends make Eden uncomfortable, she is drawn to the myriad personalities — and their complex relationships. Despite their shared history, the group has an odd dynamic. “… these people didn’t even seem to know how to enjoy one another’s company,” Eden observes. Complicated jealousies, past actions and devastating secrets are revealed when one of the six is murdered.

Rader-Day expertly plots an ingenious mystery in “Under a Dark Sky.” Eden grieves for her husband but also mourns what her marriage was and what the relationship with Bix could have been. Grief and regret have turned her into a woman she doesn’t recognize, simultaneously overly emotional, coldhearted and judgmental. Although only 34, Eden feels so much older than the friends who are even more unsettled in their mid-20s.

Set in a fictional park, “Under a Dark Sky” captures the beauty of the dozens of similar nocturnal environments that thrives at such recreation areas throughout the world.