Her father worked on the Trace estate, but he was killed in a motor accident, his wife with him. She and her brother were supported by Henry Trace and raised by a nanny in an estate cottage
She was a skilled actor, she'd had to be since she and her brother, Michael Lacey, had been having an incestuous affair since they were teens and had to constantly cover it up.
In a long game, they conspired to murder Bella, the wife of the local land owner, Henry Trace during a shoot. Michael separated Bella from the group, setting her up to be shot by Katherine. Katherine then slowly wormed her way into Henry's affections and the wedding was scheduled. Speculation was that he would not have lived more than a year after the nuptials.
After their plot was found out, as part of a murder/suicide pact, Katherine ran from the wedding chapel to meet her brother in the woods where he shot her and then himself. The instrument of death in both cases was a shotgun.
She was responsible for the murder of four people.
- Bella Trace - Shot with shotgun to the chest from distance on the 26th of June 1995.
- Emily Simpson - Broken neck after being struck from behind and the scene was arranged to appear as natural causes.
- Dennis Rainbird - Throat slit with butcher's knife.
- Iris Rainbird - Stabbed multiple times with butcher's knife right after Dennis.