DS Nicholas "Nick" Henshall, alongside his colleage DS Karen Williams investigate the murder of policeman Shane Doyle. They initially arrested Eli Dingle for the murder. Eli implicated Debbie Dingle and Jasmine Thomas as being Shane's killers and Henshall and Williams arrested and charged Debbie with the murder. However, Jasmine later handed herself in and confessed to Henshall and Williams that she killed Shane. In February 2009, Henshall investigated the disappearance of Will Wylde and in May questions Cain Dingle about a break-in. He was promoted to Detective Sergeant and returned in July 2010 to investigate the murder of Mark Wylde. He and DC Laura Prior initially arrest Nathan Wylde, but release him without charge due to a lack of evidence. They then arrest and charge Ryan Lamb, but Natasha Wylde is proven to be the killer. In November 2010, Henshall investigates the theft of two horses from Home Farm and he later buys stable manager, Katie Sugden a drink. Katie's ex-husband, Andy Sugden is not happy with Katie dating Henshall and they goad each other. In December 2010, Henshall investigates the disappearance of Jacob Gallagher and he suggests to Jacob's parents Alicia and Justin that they hold a televised appeal. David Metcalfe eventually finds Jacob in an old building and rescues him, despite Henshall telling him to wait.
Katie and her housemates, Gennie Walker and Chas Dingle, received prank calls and they were later burgled. Gennie tells Henshall that she thought Andy may be responsible. On a date with Katie, Henshall mentioned his dead wife, Alison. When they went back to Katie's, Henshall argued with Andy in the street and she decided to end their relationship. Later, Henshall returned with a petrol can and started a fire at the back of Victoria Cottage. He tried to ring Katie, but she did not answer and he assumeed that she was out. Henshall hid and watched as Carl King, Andy and other residents tried to put the fire out. The fire spread and killed Terry Woods and Viv Hope when the Post Office caught alight. Henshall returned the following morning to investigate the fire with Prior and they interviewed both Andy and Carl. In the coming weeks, Katie and Henshall got back together. Henshall attended both Terry's funeral and Viv's memorial service at The Woolpack. Andy made a complaint about Henshall harassing him and reveals his relationship with Katie to his colleague Prior. Henshall was then taken off the case and he blamed Prior for ruining his chances of promotion. Henshall threatened Andy by holding his face over a gas cooker in his caravan. Henshall and Gennie go to Butler's Farm after Brenda Walker goes to confront Andy. When they arrive, they discover that Brenda crashed her car into Andy's caravan. Henshall talked to Andy's landlords John and Moira Barton and they agreed not to press charges.
Colleague Laura Prior warned Henshall to stay away from the case and that she knew that he withheld information from Katie and Carl's statements. On Valentine's Day, Henshall took Katie for a meal at the B&B and told her that he was falling in love with her. Andy arrived with Alicia to watch them and Henshall demanded that he leave. Henshall asked his colleague DC Darren Foster for updates on the case and Foster told Henshall that they have CCTV footage from the shop where the phone used to make the calls to Victoria Cottage was bought from. Henshall asked Katie to come away with him and she agreed. At his home, Katie found some newspaper clippings about his wife Alison's death. Katie asked Henshall about them and he told her that Alison died in an arson attack on their home. Katie discovers her stolen bracelet and Henshall locks the front door and starts to barricade the house. Katie realises that he is responsible for the prank phone calls, the burglary and the fire. Henshall tells Katie that he tried to save his wife and that it was his fault she died as their home was targeted by some criminals he had arrested and imprisoned. He tells her that he wanted to make up for Alison's death and that he wanted her to need him, so he started the fire at her home in order for him to rescue her. Henshall insisted that Terry and Viv's deaths were accidental. Katie demanded that he let her go but he refused, telling her that he loves her and insists that she loves him. Katie tries to escape, but Henshall stops her. Prior and Foster call round to question Henshall after discovering he is responsible for starting the fire and realise that Katie is in the house. Prior calls Katie's phone and Henshall answers and shows them Katie at the window to prove she is alive. He produces a gun and Katie begs him not to use it and he suggests killing them both in order for them to be together. A shot was fired and Katie fled the house. She told Prior and Andy, who arrived at the scene with Gennie, that Henshall had killed himself.