Disclaimer: How I wish I owned them! Anyway, I don't; they're the property of the BBC.
He was just a boy, and afterwards others would say he'd been imagining things, but Clive was always certain what he saw that day. The tendrils of ivy wrapping themselves around his scout leader's neck; the couple who appeared and wrested the thing away; the blue police box disappearing into nowhere. Even though the leader (quite recovered, though nursing a nasty bruise around his neck) swore blind he'd just got caught up, Clive knew what he'd witnessed. The plant had come alive, had attacked the group, would have succeeded had the strangers not rescued them.
It took the threat of a psychologist and sustained bullying at school for him to stop insisting that he was right, and he subsided into a lonely silence. But in private, after school and on weekends, he scoured the microfilm archives at the library, spent his pocket money on copies of the weird stories. He kept a file under his bed that, in a few years, had grown into a box. One box became two, and four by the end of university. Only the appearance (late) on the scene of girls tore Clive's attention away from his search for the man in a leather coat, and the ivy incident was pushed to the back of his mind for the first time in a few years.
Some years later, Clive discovered the internet, and about the same time the old boxes of yellowing paper surfaced in the attic. His wife scoffed, but Clive's interest was rekindled. He knew what he'd seen and his dreams – or rather his nightmares – were once again woven with the strings of ivy, the man's blue light, the sound of the police box.
They had arguments about it. They argued after Rose Tyler had visited, with her own tale of seeing the man Clive now knew as the Doctor. His wife thought it was madness. Clive, suggesting a late-night shopping trip, was certain it was not.
He never found out that he was, and always had been, perfectly sane.