The Gallaghers' return for a fourth series, and its Lip's 18th birthday but not all is going to be clean sailing as there's a few surprises ready to hit him. First the Maguires expect him to do something for them. But the biggest shock of all is his long-lost mother Monica turning up out of the blue with a bombshell that could turn their lives upside down.

Frank is desperate to keep the fact that he is still married to Monica from his "new wife" Sheila. But Monica continies to sexually pursue him. Knowing she has competition for Frank, Sheila teams up with Debbie to reunite Monica and her lesbian lover, Norma. Meanwhile, Jamie Maguire is released from prison after serving ten years for cuddle. To his family's shock, he intends to go straight and wants no part in the family business. Instead, he gets a job at the Jockey. But he immediatly clashes with Karen Jackson, whilst Carol launches a "Free Kev and Veronica" campaign.

Monica manages to seduce Frank and sink her claws back in, but he dare not tell Sheila that he and Monica have been sleeping together. Sheila proves to be a frightening adversary when scorned and Frank could be in real danger. But neither Sheila nor Monica want to share him and he has to decide on which wife he wants. But who will he choose?

Ian gets more than he bargained for when a new person enters his life. Another passing in the Maguire household causes Mimi to think the family may be cursed.

Debbie's glad to have her dad back at home, but Monica's not happy with all the attention Frank is giving her and tells her it's time she found herself a boyfriend. Also Ian catches the eye of someone he least expected.

It's Monica's birthday, and Carl is desperate to have his family together. But that means getting rid of Monica's ex-girlfriend Norma - for good. Meanwhile, Frank gets a job working on the Maguire's ice cream van that they use to deal drugs from. It's going well until the van is stolen by an angry mob with a score to settle. Frank and Shane must get the van back before Paddy finds out, whatever the cost. Elsewhere, Mimi kidnaps Karen after her meddling results in Karen calling off the wedding and tries to bully her into changing her mind, whilst Lip is left with an unusual side-effect after being tasered by Carrie, and Kelly Ball returns to Chatsworth and moves in with Lillian.

A series of explosions spark fear that there is a terrorist at large in Chatsworth. But with all the passings in his family lately, Paddy fears the Maguire's are under attack. However, he has bigger problems to deal with when Shane and Mickey lose a box of semtex meant for some dangerous associates. Meanwhile, Frank and Monica's marriage becomes strained after a secret from the past resurfaces. Monica begins sleeping with Norma. Seeing Norma is splashing the cash, Frank attempts to steal it. But when this fails, he finds himself in court accused of sexual assault - and his only way to clear his name could cost him everything, whilst Yvonne sets up a call centre and recruits Lip and Lillian to help.

Learning of the passing of his three ex-cell mates is sending Paddy round the bend. With the three of them taken out one-by-one in suspicious circumstances, could this mean he's next in line?