Sleep So Deep — Victoria A. Brownworth

Harper and Siobhán were so happy. Siobhán was about to give birth to the couple's first child. Then a family tragedy propels the couple from Brooklyn to Dublin, ending in shattering loss for Harper when Siobhán and their baby are found dead -- victims, Harper is told, of Siobhán's crushing post-partum depression.

A riven Harper returns to New York, throwing herself into her work -- a book on an infamous lesbian murder. At a grief seminar Harper meets Quinn Murray, a transplanted Dubliner like Siobhán, and discovers a shocking coincidence between her loss and Quinn's.

As Harper gets closer to the answers she seeks, she finds her own life is in peril.