A Goodreads user asked:
Who did it? Stanley, repairman, Alex, or Ralph?
Meggin Dail I thought it was pretty clear it was the repairman, that's who Alex says she was meeting with. I feel like Alex may have even watched...
This answer contains spoilers… (view spoiler)[Stanley creeps me out with his photos and love of young girls. Maybe he is assuaging his guilt by getting Julia a modeling contract and to keep her quiet. Plus when Marc asked about the photos he had to think fast how to explain them. But how could Julia be ok with being near him now? Help it's driving me nuts! (hide spoiler)]