The Corpse with Four Wives. Purgatory Falls Mysteries, #5

Mermaid Brooke is settling into her small town life pretty well when her sister shows up with all of Brooke's possessions from their mother's home and a plan to snag a man while in town. But Brooke is distracted by the fact that the host whose party she attended with Aiden ends up dead and one of his four widows asks for help, mermaid to mermaid. But when it turns out that everyone involved with the dead polygamist was hiding secrets and her own sister has set her eyes on Aiden, Brooke is pulled in every direction.
With everyone around Brooke talking about what love means, the biggest mystery might be the question of what her heart really wants.