Leslie Coulson was introduced as a strikingly beautiful, yet devious attorney. As it turned out, she and David Hayward shared a past together.
Leslie proved her legal prowess by representing several key Pine Valley residents. She represented Jake Martin in his custody battle for Colby, Liza's daughter. He mistakenly believed that the child was his. Leslie did her best to represent her client, but when the truth came out the case was dismissed.
Leslie laid low for many months (to accommodate actress Colleen Dion's maternity leave). When she reared her head again, though, her role in Pine Valley became much more prominent. David played upon a childhood crush that Leslie had for Tad, hoping that Leslie would cause trouble for Tad and Dixie's marriage so he could have Dixie for himself. At a yacht party, David laced a punchbowl with Libidozone, a drug to increase a person's sexual desires. Leslie and Tad both gave into temptation and had a one-night stand in one of the bedrooms on The Fidelity. Leslie, however, refused to give up on Tad and insisted that their affair was not a once and done deal. She set-up an elaborate scheme to make it look as though she and Tad were lovers, a plan that included stealing some of Tad's belongings and planting them in a hotel suite that she used Tad's credit card to pay for. The crowning moment, though, came when Leslie placed a picture of herself over Dixie's in a photo from Tad and Dixie's wedding.
As Tad continued to insist that he and Leslie had no future together, Leslie took to stalking Dixie. In what was to have been the final confrontation, Leslie ordered Dixie to jump from the Chandler Building or risk having harm done to her son, Adam Junior. Leslie and Dixie struggled, but David showed up just in time to save Dixie from falling off the balcony. Leslie tried to make an escape, but lost her footing. David tried to hold on to Leslie to prevent her from falling, but he couldn't - or decided that he wouldn't - hold on. Leslie fell from the building. It was believed that she was dead, but in a stunning turn of events, Leslie was wheeled into the hospital - very much alive; an awning had broken her fall.
David tried to convince Pam, Leslie's sister, to pull the plug on Leslie, saying that she'd never be the same again. Then mysteriously, Leslie disappeared from the hospital. Gordon Feimster, a lab tech that David had bullied into helping him with his Libidozone caper, took Leslie from the hospital and kept her holed up in an old theatre warehouse so that no harm could be done to her and so he could get revenge on David for ruining his career. Leslie recuperated rather quickly, but her love for Tad remained. Tad was lured to the warehouse where Leslie planned to get Tad to marry her. Leslie had lost touch with reality and Tad convinced her that they were still in high school and planning to go to the prom together. Leslie donned a dress and Tad took her to the hospital for treatment.
At the hospital, Leslie tried to off David, after she was taken to the hospital with a broken hand. She successfully gave him an overdose of painkillers, but David didn't die. Leslie was locked in a special wing of the hospital until a transfer to the Oak Haven sanitarium could be arranged.
On the eve of her transfer, Leslie diverted a guard's attention and opened canisters of anesthesia, knocking out everyone in the hospital emergency room. She used an oxygen mask to prevent herself from falling victim to the gas. Then, using a flare gun left by another patient, Leslie ignited a fire and fled the hospital still wearing her hospital gown and slippers.
Leslie was eventually captured and sent to a mental institution for treatment. Tad later arranged for her to have her released early because he wanted to use her in a plot to enact revenge on David Hayward. Leslie drugged sister and caregiver Pam and escaped to Pine Valley. There, Leslie clobbered Tad and held him prisoner. She verbally accosted him for having gotten back together with Dixie and threatened to kill him. Leslie placed a noose around Tad's neck and readied to hang him. However, the cavalry arrived just in time to save Tad from dying. Leslie was carted off to the police station and locked away for what can only be assumed to be a very long time.