2014-2017: Occasional visits to Emmerdale
After becoming concerned for her unborn child in January 2014, Priya Sharma saw Dr Cavanagh following her body continually rejecting food. Dr Cavanagh told her that her baby was fine, but he was concerned for her health. He tried to give Priya the number for a support group but Priya refused to take it.
Later in January, Val Pollard called Dr Cavanagh out to Pollard's Barn to examine Eric Pollard who she was concerned had contracted HIV. The doctor examined Eric and came to the conclusion that Eric had flu.
2018-2019: Relationship with Bernice Blackstock
Liam was put on the judging panel for the Hotten Retail Awards and David Metcalfe tried sucking up to Liam, desperate to win the award. Maya and Liam had marital problems and Maya instigated an affair with David. Liam found out and declared he wanted to divorce Maya. Liam developed a hatred for David and took pleasure in telling him that his estranged wife Tracy Metcalfe had aborted their baby - infuriating Tracy who threatened to report him for breaking patient confidentiality.
Liam decided to sell their house, throwing Maya onto the street as the house was in Liam's name. Liam moved in temporarily with a friend until their house was ready, which Liam's daughter Leanna was not happy about. He began an affair with beautician Bernice Blackstock. Liam encouraged Bernice to break up with her boyfriend Daz Spencer so they could stop sneaking around, but Bernice was reluctant to as Daz relied on her and she didn't want to hurt his feelings.
He proposed to Bernice in July 2019 (during the Wild West Brawl), and Bernice accepted. They planned to get married but were unable to do so as Charlie was involved in a car accident and left in a critical condition, causing Bernice to leave the village and go to Australia to support her daughter Dee Dee.
2020 to present: Relationship with Leyla Harding
On 2nd January 2020, Leyla and Liam shared a kiss in Beauty & Bernice. Liam immediately felt guilty and called Bernice to confess his infidelity, causing her to end it with him. Liam tried to get Bernice back but to no avail. He told Leyla that it was best they kept their distance but agreed to still be friends.
In February 2020, Liam asked Leyla to give their relationship a go and not care what others thought. However, they soon decided to keep their relationship secret as Liam was not ready to tell Leanna yet.
- Liam only appeared as a recurring character between 2014 and 2018. In June 2018, it was confirmed that McPherson had been promoted to the regular cast. The news came shortly after the character's wife and daughter were introduced.
- Despite his first name being confirmed as Liam in Episode 7161 (20th April 2015), he was credited as Dr Cavanagh until Episode 8291 (19th October 2018) after he was made a regular.