Alyah Marsh (previously Davies) was once the best friend of Avril Powell, she appeared briefly in Episode 16 of Series 8. Alyah had a secret affair with Avril's husband Jackson many previous that resulted in the birth of a son, Dee. Alyah told Jackson that she was pregnant but he demanded she have an abortion, she agreed but decided not to go through with it and raised her son alone. Though Jackson and Alyah's affair stayed a secret at the time it happened and didn't result in Jackson leaving his wife it must have been serious, as Alyah reminded him how he had once told her he would love her forever.
Alyah married a man named Leo Davies and that was who Dee thought was his father Leo left Alyah for her sister Shona and Alyah changed her surname to Marsh.
Many years after the couple parted ways, Dee unknowingly walked into his father's life as the boyfriend of Jackson daughter Letitia. When Jackson realized the truth he attempted to ensure Dee walked out of his life without anyone discovering the truth. Jackson enlisted the help of Carl Gallagher to spike Dee and plant him at Lillian's Brothel where he would have sex with Kelly Maguire and Carl could pretend to have seen him enter. Jackson hoped this would cause Avril to demand Dee keep away but the plan backfired when Dee woke up crying for Letitia and Kelly realized what was going on, she took him to the Powell house and said he must have been spiked and walked in out of confusion.
Jackson decided to escort Dee home and took the opportunity to speak to Alyah. She expressed a complete lack of concern for Dee and Letitia incestuous relationship, stating they weren't breaking the law as Jackson's name isn't on Dee's birth certificate. Alyah attempted to seduce Jackson though he pushed her away and branded their affair a mistake, she also made various insulting comments about Avril with Jackson eluding to some kind of fight between the two women by claiming Avril "hated her guts". Alyah convinced Jackson to continue drinking with her while they caught up and he woke up the next day in her bed, though she admitted later that they did nothing but sleep.
The truth about their affair and Dee's parentage was soon revealed to the Powell family and Dee himself however when Avril saw a message from Alyah on Jackson's back (see left). Since Avril didn't realize Alyah was involved and had seen the reverent looks Jackson had been giving Dee along with the fact his real first name was Africa, Avril assumed her husband was having an affair with him! She eventually lost her temper when she found the two weight lifting together in a suggestive pose but while she was accusing them Alyah arrived. Alyah announced the truth to the family and though Avril forgave her husband, Dee and Letitia weren't ready. They first pretended to have run off to get married before returning and claiming Letitia was pregnant with Dee's baby, these were of course lies to teach Jackson a lesson. The siblings were disgusted by how Jackson was happier to drug his son than admit the truth. Dee told Jackson that he had survived so far without him and would be fine to continue without him and though Avril kissed him and told him he was welcome there any time, Dee said he thought that would cause too many problems and left.