Zero at the Bone by Jane Seville (known on the internet as Madlori) began life as very AU Brokeback Mountain fic. Now it is a solid and solidly enjoyable crime drama/gay romance novel. Jack Francisco is a doctor living in Baltimore whose life is turned completely upside down when he witnesses a mafia-related murder, agrees to testify and is forced into a Witness Protection Program while waiting for the trial. D is a hit man hired to kill Jack before he can present his evidence. Things don’t go according to plan for either of them.