Help him feel safe first, and keep the explanation brief. A child can know a story is invented and still feel frightened when the lights go out. Childhood fears are common. Sympathy and gradual practice help more than pressure to be brave. [American Academy of Pediatrics](https://www.healthychildren.org/English/health-issues/conditions/emotional-problems/pages/Understanding-Childhood-Fears-and-Anxieties.aspx)

You could say:

> “That story really frightened you. Slender Man is a made-up character. Sometimes our brains keep sounding a danger alarm after a scary story, even when we’re safe. I’ll help you get comfortable sleeping here again.”

I’d leave out the discussion of why he collects children or how teleportation might work. Those questions encourage more speculation about the character. Copying and transporting a person isn’t an established scientific capability, but you don’t need to get into that to explain that the story is fiction.

- Talk during the day, when bedtime isn’t looming. Listen to what worries him, whether it’s being alone, a window or a shadow. Avoid ridiculing his fear or repeatedly debating the monster’s powers.
- Make a bedtime plan together. Follow a familiar, pleasant routine and read a comforting book. A nightlight or an open door may help. Practise a few slow breaths together.
- Sit nearby at first while he settles. As that gets easier, move toward the doorway, then switch to brief, predictable check-ins. Choose manageable steps together and praise his effort, even when he still feels nervous. The [American Academy of Pediatrics](https://www.healthychildren.org/English/health-issues/conditions/emotional-problems/pages/Understanding-Childhood-Fears-and-Anxieties.aspx) recommends gradual approaches to childhood fears.
- Help him practise saying, “I don’t want to hear scary stories.” If the other child keeps deliberately frightening him, involve the teacher. Avoid further frightening videos or searches for now.

You can’t prevent every fright. With your support, he can learn that frightened feelings pass and that he can cope. Regular routines, listening and simple relaxation are also consistent with [NHS guidance on childhood anxiety](https://www.nhs.uk/mental-health/children-and-young-adults/advice-for-parents/anxiety-in-children/).

If his distress persists, worsens or substantially disrupts his sleep or daytime life, speak with his pediatrician or a child psychologist. Seek help sooner if he’s already struggling badly.