Lucy and her husband, Adam, have been best friends with another couple, Cora and Scott, for years. The four are practically family at this point--they vacation together, co-own a beach cottage, and their young children are inseparable. So Lucy is devastated when, while looking at a colleague's photos of a trip to the Maldives, she spots a picture of Scott, apparently on a luxurious holiday with another woman.

Lucy is determined to protect her best friend from her husband's seeming infidelity, but when she learns that the woman in the photo has gone missing, she can't help but fear that Scott was involved. As she searches for answers, she uncovers secrets about her friends and her own husband that could destroy the wonderful lives they have built...and she suspects that everybody around her knows much more about the missing woman than they are letting on. Is Lucy actually the one most in the dark? If so, what are the consequences of discovering the truth?