Lachlan has been involved in some storylines; sexually assaults Alicia Metcalfe, accidentally shot his grandfather, his longstanding feud with Robert, being kidnapped by Aaron Dingle after Lachlan threatens and lie about Robert sexually abused him before being involved in the crash that killed James Barton, causes the crush which killed Chrissie and Lawrence and left Rebecca brain damage, murdered his best friend Gerry Roberts by bashing him with a rock, trying to kill Robert and Liv Flaherty and kidnapped his aunt Rebecca White before held her captive.
Lachlan befriends Belle Dingle but her strange behaviour causes others to think Lachlan has been harassing her. Lachlan photographs Belle and realises that something is wrong with her. He helps her realise that she needs help, as do her family. Lachlan also makes friends with Jacob Gallagher and spends time with him at his house. Jacob's mother, Alicia is friendly with and feels sorry for him as she can see he is a bit different. Chrissie is grateful for this but it soon becomes clear that Lachlan's interest in Alicia is inappropriate as shown when Chrissie finds that Lachlan has a lot of photos of Alicia. He claims that this is because he is helping Jacob make a photo book, which is true, and Jacob gives it to his mother as a present.
Lachlan begins to imagine things about Alicia and thinks that he loves her. He later buys Alicia an expensive handbag as a Valentines Day present but doesn't let on that it's from him, making her husband, David Metcalfe, wonder where it came from until Nicola King tells him that she saw Lachlan with it. David tells Alicia and she returns it, letting him down gently, but Lachlan ignores it and David's warning to keep his distance. Believing Alicia returns his feelings, he sexually assaults her but distraught, Alicia throws him out of the house and calls the police. He initially tells the police that their relationship was consensual and that they were a couple, leading her to be questioned about this. Chrissie initially believes him but later finds evidence that he is lying and on hearing Alicia's version of events, calls the police herself. She tells him and her father that Lachlan must take responsibility for what he has done. And after being kidnapped by Alicia's husband David he confesses that their relationship was all in his head and that he did assault her, he apologises to Alicia and her family for what he has done and is put on the sex offenders list for 2 years.
After finishing his counselling, Lachlan begins suffering abuse from other students. He starts to blame Chrissie for ruining his reputation. Chrissie decides to get in contact with his father Donny in order to get through to him. Donny suggests to Lachlan that he'd live with him to which Lachlan agrees. The next morning, Chrissie and Lawrence tell Lachlan that Donny had left to go abroad when in fact, he had been beaten up by loan sharks. After nearly being beaten up from other students and was saved by Alicia, Lachlan finally showed remorse and apologized to Alicia. A few weeks later, Lachlan goes to stay with Rebecca for a few weeks. He returns, aware of Robert's cheating, and becomes resentful towards him. After Chrissie is arrested for causing the helicopter crash, Lachlan becomes determined to kill Robert and gets a gun from the safe. Lachlan walks with a gun around the village and is informed by Rakesh Kotecha. That evening, Robert is shot and falls into a coma. After Lawrence confesses to attempted murder, Chrissie arranges Lachlan return to Rebecca for a few months. Upon his return, he and his step-aunt Gabby Thomas rob Eric Pollard's house and steal Val's wedding ring.
In June 2016, Lachlan used a spy machine to watch Belle. When Lachlan did use it, he saw Belle trying to kiss Dr Bailey but he refused to, so Belle left him. He took screenshots of the footage and sent them to his phone. The following day, he met up with Belle's half brother Cain Dingle in The Woolpack to show him the photos. Cain demands that Lachlan to Bluetooth the photos to his phone. Later on in the month, Lachlan broke into Dr Bailey's and started to smash up the sitting room and the kitchen and them was joined by Belle who refused to smash their wedding photo. Dr Bailey and his wife Angie return home and both Belle and Lachlan made a run for it. Belle went back tho get her bag but got caught in the act.
2016-2017: Shooting Lawrence and imprisonmentEdit
After everyone finds that Lawrence may be gay, he throws Chrissie and Lachlan out for good. Diane Sugden let's them stay at the B&B for a bit. Lachlan stole one of Lawrence's cars and drove around Emmerdale in it. He skidded to halt in a field, nearly running Lawrence over. Lachlan starts to question Lawrence about why he threw him and Chrissie out. Lachlan thought he was in a tantrum just because he is gay. Lawrence slaps Lachlan in the face.
At the end of July 2016, on his 16th birthday, Lachlan broken his way into Home Farm and held Lawrence hostage with a shotgun. Lachlan ordered Lawrence to text Chrissie to say that he is sorry. After that, Lawrence wrestles with Lachlan to try and get the gun, but Lachlan accidentally pulls the trigger, shooting him in the stomach. Chrissie rushes in and tells Lachlan what to do. At the hospital, Chrissie and Lachlan are told that Lawrence has lost a lot of blood, so they need to take him into theatre and start and operation. It was found out that the gun was planted in the car of Robert's brother Andy. Andy was sent to prison and charged with attempted murder. He then later escaped and went on the run, with the help of Rakesh Kotecha, Robert and Bernice White.
In October 2016, Lachlan gets kidnapped by Robert's boyfriend Aaron Dingle after Lachlan threatens to lie and tells everybody that Robert sexually abused him. Aaron and Robert took Lachlan to the quarry when he escape and Aaron and Robert chase him. Lachlan nearly pushes Aaron over but Robert grabs him. Lachlan tells Aaron that Robert used to sleep with Rebecca when he was with Chrissie. Aaron and Robert put Lachlan back in the car boot. Later, Robert and Aaron have a chat when they see Ashley's wrecked car. Aaron avoids hitting the car but crashes into a lake. Robert rescues Aaron and went back for Lachlan who managed to make his own escape. Robert comes out of the lake and gets angry with Lachlan. Robert threatens Lachlan if Aaron dies, he will come after him however, Aaron surivies. A week after, Lachlan lies to his family where he was, making them unaware that Lachlan was involved in the crash that killed James Barton.
In November 2016, Lachlan finally confesses to the police that he shot his grandfather Lawrence but covers his mother's involvement in framing Andy. Lachlan's family left shock when learn Lachlan had been charged with attempted murder and perverting the course of justice.
In January 2018, having become tired of his family, Lachlan blackmails his family into getting him a place with Belle Dingle, or he will tell Robert that the family plans on moving to Australia with baby Seb. However, Lachlan is horrified when Belle breaks up with him.
When he finds out it was Chrissie's doing, he goes to confront her, but finds his whole family about to give chase to Robert in a car when he snatches Seb. Lachlan reluctantly joins them. While going down Skipdale Road, Lachlan suffers a mental breakdown and tries grabbing the steering wheel, sending the car into the path of a incoming lorry. The car overturns and crashes into a field, killing Lawrence instantly, as he didn't have his seatbelt on trying to pull Lachlan away from the steering wheel. Chrissie is trapped in the front seat and dies minutes later from a serious head injury.
Rebecca also has a serious head injury but slips into a coma and is rushed to hospital. She is treated for in an ICU. One month later, Rebecca wakes up from a coma and can't remember a thing about the crash. She suddenly remembers days later, but Lachlan manipulates her into believing that Chrissie lost control of the car. The nurses say to Robert that Rebecca's memory has been affected due to her head injury.
In May 2018 Belle goes missing so he and friend Gerry Roberts go looking for her, as Lachlan becomes increasingly worried he says he doesn't want anyone else to die because of him Gerry takes notice of this and thinks it suspicious so makes it his priority to find the incriminating voice mail Lachlan sent him the day of the White crash. He eventually recovers it of his computer and listens to it horrified. He later confronts Lachlan to which Lachlan tells him not to tell anyone. As Lachlan becomes increasingly worried that Gerry will let his secret slip as Gerry makes jokes relating to the crashighest, he lures Gerry to the B&B which was under renovation and tells him to go over to get one of the beer kegs when Gerry does this Lachlan kicks another keg over to the scaffolding where Gerry is which knocks the scaffolding down and the floor falls in. Gerry doesn't lose consciousness and probably will survive and is begging Lachlan to phone an ambulance but Lachlan ends Gerry's suffering by hitting him over the head with a rock.
- Lawrence White, 11th January 2018 - Killed during car accident caused by Lachlan.
- Chrissie White, 11th January 2018 - Died after car accident caused by Lachlan.
- Gerry Roberts, 17th May 2018 - Crushed under the B&B's collapsed roof & bludgeoned with a concrete block to finish him off.
- Conman, 13th July 2018 - Unknown method of murder.
- Lawrence White, 26th July 2016 (accidental) - Shot by Lachlan during a struggle.
- Rebecca White, 11th January 2018 - Survived car accident caused by Lachlan.
- Rebecca White, 25th January 2018 - Attempted to suffocate her in hospital but couldn't go through with it.
- Robert Sugden, 17th July 2018 - Poisoned with carbon monoxide.
- Liv Flaherty, 17th July 2018 - Poisoned with carbon monoxide & thrown against a wall, causing her to hit her head on a plug point.
- Rebecca White, 17th July 2018 - Bludgeoned with screw driver.
"We both know what happened to them, don't we?" (before murdering Gerry with a rock)