Once she gets downstairs, she finds her mother, played by Corinna Marlowe, eerily and aggressively rattling the door handle, trying to get outside.
As she approaches, her mother, Patricia, turns around, and it's at that point that Emma properly wakes up. It turns out she's been sleepwalking, and it's not her mother rattling the door handle, but it is in fact her.
You can watch the full, ominous clip right here now.
Based on the novel of the same name by Sarah Pinborough, the series follows Emma as she starts to fear that she's losing her mind and stops sleeping a couple of weeks before her 40th birthday.
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Emma realises this is just what happened to her own mother Patricia, who stopped sleeping just before she turned 40, and who suffered a violent psychotic breakdown on the night of her birthday.
Patricia always told Emma that she would go the same way, and to find answers, Emma starts to investigate the truth of her painful past.
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Insomnia comes from production company Left Bank Pictures in association with McClure's Build Your Own Films, and when it was first announced, McClure said: "Myself and BYO Films are really excited to be working alongide Left Bank on Insomnia.
"It’s a very different role for me, Sarah Pinborough has written such an exciting script. We have a fantastic cast, crew and production team all set for a very fulfilling few months ahead!"
Insomnia will debut exclusively on Paramount Plus in the UK on Thursday 23rd May.
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