Why did Tom cut his fingernails at the end of Deadwater Fell? That confusing final detail explained

Here's what you need to know about the fingernail cutting in Deadwater Fell, as fans are perplexed by this final detail.

Originally airing on Channel 4 back in 2020, Deadwater Fell is the new series that everyone is talking about which stars David Tennant as the lone survivor after his wife and three children are murdered. Deadwater Fell is proving to be one of the best thriller series added to Netflix, with viewers eager to race towards Deadwater Fell's shocking ending and trying to find more about where Deadwater Fell is set. The series is delighting and shocking fans, but some have been a little surprised by the final moments, particularly the fingernail clipping scene. Here's what you need to know...

*Warning, there are spoilers ahead!

Why did Tom cut his fingernails off in Deadwater Fell?

Toward the ending of Deadwater Fell, it becomes clear that Tom was responsible for the death of his wife and three daughters and had injected them with something and then set the house on fire.

As Tom sits in his bedroom we see him snipping his fingernails obsessively until the skin around them is bleeding. This confused fans who thought perhaps he was removing some kind of evidence or a way of linking himself to the murders. So why was he trimming his nails until he bled?

Tom was pictured cutting his nails back like this to highlight how obsessive he is, even when it's causing him pain. His need for perfection at any cost was highlighted in this action and foreshadowed that he was the type of man who was able to commit a homicide and murder his wife and children.

His other obsessive tendencies are highlighted at other parts in the series, including the way he scrubbed his hands, and the persistent need to flatten his hair, a metaphor for wanting to appear perfect on the outside.

Why did Tom kill Kate and the children?

The answer as to why Tom killed his wife and children was explained in the flashback to the night Kate and the three girls died. In the scene, Tom confronts Kate about wanting to divorce him, after he finds a voicemail from solicitors calling about her divorce options and another voicemail about redirecting her money so that Tom wouldn't have access to it.

"You won’t get the kids. I am going to ruin you, I'll f**king ruin you," Tom shouts at her during an argument witnessed by their daughter which scares her and leads her to run into the garden - explaining the pine needles in her feet. He accuses Kate of having an affair with Simon, highlighting that his jealousy and need to control things were the motive behind his actions.

It's revealed that Tom organised the whole thing and asked Kate to buy a padlock and bought insulin back from work so that he could kill all four of his family members. It was a deliberate act and he planned to kill himself along with his family.

Did Carol know all along?

It is revealed that Carol likely had a good idea about Tom's actions all along.  "I just wanted you to know I tried my best. I did my best mum. Bye," he said when he called her on the phone.

The creator of the show, Daisy Coulam, spoke about why Carol didn't say anything to the police and chose to protect her son, despite his horrific actions. "When you realise that somebody in your life is toxic, it takes an awful lot of courage to speak up and I suppose she sits into that theme of communication and openness. She needs to admit to herself that her son has done this terrible act," she told Radio Times. 

"When you say things out loud, sometimes that’s the hardest thing. Basically, in that last episode, all of our characters are saying things that they’ve just been unable to say. Actually, only by doing that can you move on," she concluded.