Finn interferes with Susan Kennedy's (Jackie Woodburne) multiple sclerosis medication, resulting in her hospitalisation and his subsequent promotion to principal.

Finn returns to Erinsborough with Elly's sister Bea Nilsson (Bonnie Anderson), who believes him to be a disabled man called Patrick, in order to exact his revenge.

Mills was promoted to the regular cast in March 2019 and Finn was redeemed through an amnesia storyline, which saw him move in with the Kennedys and start a new relationship with Bea.

On 15 November 2016, Sophie Dainty of Digital Spy reported that actor Rob Mills had been cast in the guest role of high school teacher Finn Kelly.

[5] Finn is hired by Erinsborough High principal Susan Kennedy (Jackie Woodburne) to replace teacher Brad Willis (Kip Gamblin).

[9] Finn begins tutoring Elly's student Xanthe Canning (Lilly Van der Meer) and shows interest in her cousin Ben Kirk's (Felix Mallard) career plans.

A writer for TV Soap said that relocating to Erinsborough to work at the high school was all part of Finn's plan to win Elly back, after ruining their relationship with his "vindictive scheming".

[13] The next step in Finn's plan sees him interfere with Susan's multiple sclerosis (MS) medication, resulting in her hospitalisation and his promotion to acting principal.

[16] While shooting the medication swap scene, the director asked Mills to make it clear that Finn did not find his decision easy, showing that he was not all bad and had chosen "the darker path" as it was the quickest way to achieve his goal.

Johnathon Hughes of Radio Times observed that Finn is "borderline grooming" Xanthe with his manipulative behaviour, and Mills admitted to being worried about how far his character was going to go with her.

Mills told Johnathon Hughes of Radio Times that viewers would be left wondering whether his feelings for her were genuine, pointing out that she looks a lot like Elly, which is easier for his manipulation.

[28] Finn's revenge plan is revealed on the day of a local scavenger hunt when he deliberately strikes Xanthe with Elly's car, before kidnapping three of his victims.

[34] The producers also chose to introduce returning character Beverly Marshall (Shaunna O'Grady) into the storyline, as she carries out a series of tests and concludes that Finn's amnesia is genuine.

[36] Bea plans to tell Finn how much he hurt her, but when she sees him save Imogen and Susan from a speeding car, it causes her to change her mind about him, leaving her conflicted when it comes to his sentencing hearing.

[39] Finn and Bea's feelings for one another are revealed when he deals with an obsessive fan, Alfie Sutton (Harry Borland), who has broken into the house to take a photo with him.

He told hosts Sarah Harris and Tristan MacManus that he had been on set for the filming of the final scene, but did not confirm at the time whether he would be reprising his role.

While Susan is in hospital, Finn becomes acting principal and he attempts to force Elly out, after learning she spoke to his wife, Miranda Kelly (Dajana Cahill).

When Bea comes home early and finds Finn's empty wheelchair, she calls him in a panic and he tells her that he has been regaining movement in his legs, but fell when he went out.

All of the physical evidence in Finn's case is destroyed in a fire, so Shaun tries to convince him to change his plea, but his lawyer Imogen Willis refuses to represent him at his sentencing hearing if he does.

Finn is accused of planting cyanide canisters at the community centre during the Sonya Foundation launch; however, Ned Willis comes forward and reveals that Harry is responsible.

He startles student Olivia Lane (Grace O'Sullivan), who goes missing shortly after, forcing him to confess to the police and costing Elly her job.

Finn helps deliver Elly's daughter Aster Conway (Isla Goulas; Scout Bowman) while they are being held hostage by Robert Robinson (Adam Hunter).

Finn is invited to Elly's 35th birthday party on Pierce Greyson's (Tim Robards) island, after Toadie agrees to act as his guardian.

Toadie finds the dinghy that Bea supposedly took off from the island, so Finn hits him with a rock, places him in the dingy, punctures the bottom of it and pushes it into the sea.

Finn reappears as Susan watches his video diaries and visualises him, so she can understand his state of mind and motives for the events that led up to his death.

"[55] In his assessment of the character, Johnathon Hughes of Radio Times found that "on the surface, handsome Finn is charming, charismatic and an excellent addition to the school".

[57] Similarly, Radio Times' Simon Timblick opined "after all the terrible things Finn Kelly (played by Rob Mills) has done in Neighbours, you'd think he’d be thrown in prison for a ker-zillion years.

"[58] However, Charlie Milward of the Daily Express said the redeemed Finn "has proven to be a reputable young man", whose "charismatic ways" made Bea fall for him again.

"[59] But McMullan said while the plot was not perfect, the conflicts were "fresh ground" for the show, while "the moral grey area that the story has been exploring is an interesting one – and certainly caused a lot of conversation.

[59] He concluded that the character's amnesia had potential for several future storylines, adding "Could he end up being one of the finest residents Ramsay Street has ever seen or will we find out that a leopard can't change their spots?