It was not in an explosives cupboard, and he didn't know. Basically this was in an HE building being converted over to a young offenders institute, and for whatever reason, all the science teachers quit en masse as the switch was happening, leaving all their students in the lurch. So one morning he came into work, was told he was being promoted to Technical Demonstrator, given a Bunch of Mysterious Keys, and told he had three hours to familiarise himself with the contents of the chemical cupboard.
"Great," he said. "Where is the chemical cupboard?"
"Shrug emoji," his boss said gravely, and wandered off to have crisps.
So he spent an hour wandering the building and trying his keys in every lock before finally finding a door that opened, and upon finally opening it, was immediately greeted by a Tesco carrier bag on the floor labelled 'Asbestos, do not touch'.
"Right-o," he thought. "No touching that."
But then he had two hours left to familiarise himself with the packed shelf contents of quite a large room, and the problem is that when you tell an autistic lab tech to familiarise themselves with a room full of chemicals, what they hear is not "Have a quick look so you have an idea of what's there", it's "These chemicals must be catalogued in detail and also here have a time pressure," so he was going to be both Thorough and Grumpy about this. And this room was packed.
The oldest bottle he found was a reagent opened in 1959.
("It was quite beautiful, actually," he told me dreamily. "A work of art. I wish I'd kept it.")
The cyanide, when he finally found it, was in a stoppered glass vial. So that was the point he lost his shit and went and grabbed Caroline.
The kicker is, Caroline didn't care. She insisted they didn't have the money or resources to spare on getting rid of it. So he had to march all the way to the Dean's office.
"You look like you're having a bad day," she said warily.
"Well I thought it would peak with the Tesco carrier bag of asbestos I found," he said, "but I was very wrong."
And that's how you give your boss a heart attack.