1. In THE SANATORIUM, Elin Warner was on a break from her job as a detective. In THE RETREAT, she is back at work but stuck at a desk job before being asked to investigate a death at the island retreat. When Elin suspects the death isn’t accidental, DC Steed stays on to help with the investigation. How does Elin’s relationship to work, and her career, change over the course of the book? How does having a partner affect Elin? Discuss.
 
2. LUMEN is built on the same island that once housed a school for troublesome boys that burned down decades ago. Do you think the island’s transformation added depth to the story? Did you expect the events from the past would connect to the present in the ways that it did? Were you surprised by any of the twists? Why or why not?
 
3. Elin’s relationship to LUMEN is complicated. Her boyfriend, Will, is the architect, who had hoped the retreat would give the island a much-needed refresh to overcome its dark past. Do you think Elin was right to take on the job, given Will’s involvement with LUMEN and her own doubts about her performance? Why or why not?
 
4. The Leger family --- Hana, Jo, Bea, Maya --- and their boyfriends are central to the novel. As time passes and tensions rise, secrets are revealed that expose their connections are shakier than ever. Did you anticipate how their group would react? Did you suspect the intentions of anyone in the group, and were your suspicions correct?
 
5. In THE RETREAT, Elin and Will’s relationship turns rocky when Elin makes the investigation a priority over him --- or so Will thinks. Do you agree that Elin’s actions and decisions caused their relationship to deteriorate, or is Will also at fault? Do you think they will reconcile?
 
6. In the novel, the island is known locally as Reaper’s Rock because of a uniquely shaped rock formation. In your area, are there natural formations or human-made structures --- buildings or otherwise --- that have been associated with local lore or myth in some way? If so, what is the history behind them?
 
7. At the end of THE SANATORIUM, someone is ominously watching Elin from afar. In THE RETREAT, it seems as though this mysterious figure is back, intentionally tweeting at the police with threatening messages directed at Elin. Do you have any guesses as to who this might be? Discuss.