Incel

Detective Damian Arruda thought his partner was just too distraught to accept his wife's murder as a random act of violence. Then the devastated widower got too close to the truth, and now Damian is grieving his best friend. As his conscience threatens to eat him alive, he'll stop at nothing to find the killer.
Special Agent Melissa Walker's partner met a violent end as well, and his death is almost certainly connected. When she joins forces with Damian, the investigation takes them into the vile underbelly of the Internet: the incel community and its toxic forums full of misogynists who consider themselves "involuntarily celibate" and feed off each other's vitriol and hatred.
As the pieces come together, there's no denying the three deaths and the poisonous, cultlike community are part of a wave of murders, grisly assaults, and bombings. Damian and Melissa are running out of time to take the killers down before more innocent people fall victim-and before someone decides that one victim at a time isn't enough.