Malady by Trisha Wolfe

Blakely Vaughn is no longer shrouded from a world of feeling. She’s been thrust into a blinding light, emotions assaulting her, making her question her purpose and even her sanity.

When Dr. Alex Chambers, a biomedical scientist, conducted a crude experiment on her in an effort to cure psychopathy, he did more than just remedy her “sickness”; he changed the very fabric of Blakely’s existence.
Unable to trust herself to return to the life she once knew as revenge for hire, Blakely’s running from her dire crime and hunting the man responsible, desperate to force him to correct the damage. By any extreme means necessary.
Having abandoned his project when the cruel woman he fell for convinced him it was a failure, Alex has returned to the city in search of an answer. After numerous trials and failed attempts, his body count is stacking, and he’s attracted the attention of the infamous Angel of Maine serial killer—the very monster who tore his life apart and the catalyst for his research.
Now both Alex and Blakely are in danger of being eliminated by Grayson Sullivan, a lethal vigilante who has given a warning to rectify the mess. Once enemies, now drawn together in a toxic tangle of love, hate, and maddening obsession, a twisted malady of the heart will test Alex and Blakely until they’re left with only two choices: save one another…or be each other’s ruin.