Mercy has two brothers. Jeff is an agricultural super-scientist. Dustin was treating an outbreak of Pinnochiosis on Earth's moon, but was killed by the robots he was trying to treat. Mercy now has a personal vendetta against all robots because of Dustin's death.
Mercy dated Sparks Nevada while they were both in the USSA Academy, until Sparks broke up with her via mail sometime after their graduation. Before the breakup, they shared a social circle. Mercy also shamed Sparks' father, Captain Caiphas Nevada into giving Sparks his Robot Fists weapon as a graduation present.
Mercy became a bounty hunter later, and eventually was tasked with tracking down Sparks Nevada after the robot marshal Techs issued a bounty against him. Sparks initially fled from Mercy, but later she confronted him again and bonded over keeping other bounty hunter Orna Peganu from killing Sparks instead of just collecting on the bounty.
Croach declared himself under onus to Mercy for rescuing him, Sparks and The Red Plains Rider from Orna Peganu. Red left their company to find her husband, Cactoid Jim. Sparks decided to travel with Mercy to rekindle their romance, and Croach came along for onus reasons.
Mercy then took Sparks to the Bounty Hunter's guild to get his bounty hunter's license in Mutiny on the Bounty Hunter. There, she and Sparks knocked out Pemily Stallwark after she went berserk in the bounty hunter's office. Afterwards, with Croach's help doing most of the work, the three collected ninety-nine bounties in a month.
The 100th bounty was for The Red Plains Rider. Croach tracked her to the location of the Secreted City of Rococoo, where Dale Treamain and the grey-skinned martians surrounded them. Red intervened to save their lives, but Mercy was still determined to bring in Red for the bounty. Sparks drew on Mercy after Mercy drew on Red to try to diffuse the situation. Sparks misinterpreted Mercy breaking up with him as preparing to shoot him, and shot at Mercy. Croach, who was still under onus to Mercy, threw himself in front of the bullets, and Mercy took the distraction of Croach's impending death to escape.
In Personal Business, Mercy has once again come to Mars, determined to hunt and kill both Sparks Nevada and the Red Plains Rider. However, she is confronted by Croach, who has been freshly resurrected by V'stalu of the Galaxium. Croach, now at one with the universe via sharing consciousness with V'stalu, uses The Force Galactic to convince Mercy to let go of her anger towards Sparks and Red.
That forgiveness seems to be short lived, however, or perhaps died with V'stalu . In The Night We Never Met, Mercy has picked up a protege, Moon-resident Gree Skookum. Gree and Mercy stop Troubleshooter Ginny West on her way to meet Sparks for their first date. A dissatisfied customer had taken a bounty out on Ginny's head, and when Mercy saw that Ginny was currently dating Sparks while researching the bounty, she chose to attempt to exact revenge on Sparks again, as well. Mercy hacks in to the Marshal Station AI remotely and begins removing all the air, suffocating Sparks and The Red Plains Rider.
While Mercy is talking to Gree, Ginny uses her wrist device to have Troubleshooter HQ disable all of Mercy and Gree's tech, and have the bounty removed, as taking out bounties on Troubleshooters is illegal. The bounty transferred to the person who took the bounty out in the first place, forcing Mercy and Gree to leave to handle that bounty. Ginny also restores the Marshal Station Doors to functional, saving Red and Sparks, so Sparks can leave for his date with Ginny,
- The Sad, Sad Song of Widow Johnson, Part Two (SNMOM #2)
- The Sad, Sad Song of Widow Johnson, Part Three (SNMOM #3)
- One Night at O'Tooles (TAH #82)
- Mercy Killing (TAH #86)
- Mutiny on the Bounty Hunter (TAH #91)
- Red Alert (TAH #95)
- Tales of the Troubleshooters - Personal Business (TAH # 104)
- The Night We Never Met (TAH #188)