Wesley Wyndam-Pryce was the straight-laced Englishman who had a career as a watcher until Faith went postal and Buffy Summers quit. His unemployment led him to Los Angeles where he joined Angel's team in the fight against evil. Lilah Morgan was a quick-witted, intelligent attorney with a position at Wolfram and Hart - AKA the law firm from hell. At first the two may seem one of the most unlikliest of pairings however, once their interaction began the sparks flew. After Angel and Darla's son Connor began Wesley began studying everything he could about the child born of two vampires. His findings revealed a phrase - "The father shall kill the son." Believing Angel might harm the child, Wesley took him. In effort to save Connor, Wesley had his throat slashed and Connor was taken to a demon dimension. Angry, Angel and the gang shut Wesley out and treated him as though he were an enemy. Knowing he would be vulnerable, Lilah sought her prey.
She first visited Wesley at his apartment not long after his throat had been slit. She walked in though he made no secret that he did not want here there and began to undermine him. She told him she had expected flowers, cards and balloons wishing him well. She brought with her a 15th century copy of Dante's Inferno in the original Tuscan as a gift to go along with her offer of a job. They discussed that the book is a guided tour of the underworld and that the worst spot in hell is reserved for those who betray.
As Lilah's plan continued she set up tests for Wesley, seeing how far he'd fallen from grace. On one particular evening in a bar she sat down across from him and they spoke about Connor's existence. After some more mocking and threatening they found themselves in Wesley's apartment in bed together. The encounter ended with her telling him she isn't the type to pine and that he shouldn't think about her when she's gone. He countered by telling her he wasn't thinking about her while she was there.
However, as summer ended and fall came Lilah and Wesley were still having their sordid affair, thinking no one knew. However, Wolfram and Hart did know. The affair continued through Lilah's promotion and Wesley rescuing Angel from the ocean.
Though it may seem their relationship was based merely on sex, there actually was some depth to them. On one particular night, wrapped in each other's arms, Wesley referred to their affair as a relationship. It was the first time the word had been used and they'd made a bet as to who would say it first. Lilah won herself a crisp one dollar. Before taking it though she made Wesley sign it as proof that what was going on was real.
Soon Wesley's feelings for Fred began to seep through and Lilah's jealousy emerged. Wesley broke things off with Lilah to return to the good fight with Angel investigations, however intense feelings for Lilah remained. Though he'd broken up with her he still entered Wolfram and Hart to save her as it was under attack from The Beast.
When the Angel Investigations gang found her talking to soulless Angel, Wesley brought Lilah back to the Hyperion to stay with them as she was injured and homeless and being hunted by the Beast. Angel broke lose and the gang went after him, Cordelia and Lilah staying at the hotel. Angel doubled back to the hotel and Lilah and Cordelia ran. Much to Lilah's surprise, Cordelia (Who wasn't actually Cordelia) let Angel lose and before Lilah knew it, Cordelia had killed her.
Wesley, Fred, Gunn, Connor and Lorne found Lilah's body with what looked like bite marks in her neck. Fearing she'd rise as a vampire they planned on beheading her. Wesley volunteered and took her to the basement. Before he could though, he rehashed their relationship in his head with a visit from Lilah.
Thoughts of Lilah continued in Wesley until after they defeated Jasmine AKA The Devourer. Going back to the hotel, the gang found Lilah waiting for them. Obviously they were shocked since they believed her to be dead. She was dead, she was back on business from Wolfram and Hart. Her after-life contract allowed the firm to bring her back as needed. She told Angel and his crew, including an extremely disbelieving Wesley, that the senior partners were handing them the Los Angeles branch of the firm. While touring the newly rebuilt offices Wesley snuck down to files and records. Lilah had expected him but didn't realize what he was there for. He took her contract and set it on fire, intending to free her and let her rest in peace. However, the fire was of no use because her contract was found safely tucked away in the cabinet where Wesley had found it. He'd failed, but it meant a lot to Lilah that he'd even tried.