Pat Kerrigan was sentenced to life for killing her abusive boyfriend when she first came into Larkhall. She meant business e.g telling a nun to strip, beating Natalie Buxton in a fight, elevating her to "top dog".

Pat Kerrigan hated bullies, standing up for Arun Parmer, a victim of Natalie Buxton. She fought Natalie and won, meaning Arun could stay in Larkhall.

She had a sexual relationship with Sheena but when she was released on tag, this left her heartbroken.

Pat hated Natalie Buxton because she was a nonce and a bully. Pat was a victim of child abuse so she would understand what the girls went through. Natalie always denied that she was a nonce but Pat could see right through her. She got a recording of Natalie admitting her crime and played it to the whole of G-Wing; this left everyone disgusted that she could lie about such a crime. The inmates turned against her, including Darlene and Janine.

When Pat saw Natalie using a young girl to stuff drugs into the prison, she came up with a plan to get rid of Natalie once and for all. She got the help of the two Julies and Tina to make it look like Natalie is going to escape but this was all a set up. She was going to kill her on the day of Julie Saunders son's wedding. Natalie got out to the bins first but she realised it was a trap to get her into trouble for trying to escape. She and Pat started fighting; Pat reached for a rock and smashed it on Natalie's skull.

She returned to the wing after killing Natalie and made it look like an escape. Donny and Mandy realised that Natalie was nowhere to be found and they went looking for answers.

After killing Natalie, Pat couldn't believe nobody took the bin bags on the way out. She voluntered to help out the Julies while Tina was away and took Natalie out of the shed, putting her in the freezer where Julie Johnstone later found her. Pat then had to confess the truth; she told them if Natalie was alive today she would have carried on destroying whoever she touched. She had to kill her for what she had done to the girls and for the sake of the other inmates.

Pat told them she needed their help to get rid the body before she was found out. Under the noses of the guards and screws, they moved Natalie to the kitchen but she started to defrost. Pat put her in the laundry room for the time being but then she finds out that a man is coming to fix the laundry in the afternoon. Again, she moved Natalie and the two Julies helped to make it look like water had spilled on the floor. Pat had to think about where she was going to put Natalie. She finds the manhole and tells the Julies she is going to put her there. She asks the Julies who is going to stand and watch and who is going to help her drop her down there.

Julie Johnstone helps Pat to drop her down the hole but after seeing Natalie's leg she runs and vomits. Julie Saunders says she will do it instead and they pick up her body. Before Pat drops her down the manhole, Julie J says "shall we say a prayer or something?" Pat replies "rest in shit you bitch" and kicks her down.

Slyvia later believes Natalie is dead but Pat brushes it off and continues to enjoy Christmas.