One of them opened the cupboard, and the other one pushed. Montague crumpled into the dark cupboard, while the door closed behind him.
Montague blinked. Once, twice, three times, but still, nothing. His eyes couldn't seem to get used to the impenetrable darkness. He moved his hand to open the doors again, but his hand felt nothing but air. No wood, no doorknob. They must have locked it, transfigured it in some way, and so he shouted out, calling their names over and over again. No one answered.
His body was cramped in such a strange fashion - he could feel his knees by his chest, but then his feet felt like they were a million miles away, and his body generally felt larger and lighter, like it was floating. He wiggled his toes experimentally, and he couldn't feel anything - but then, after a second, they moved. A strange lag between his brain and his feet.
He could still hear Weasley laughing, and it echoed in his ears. He had only been trying to dock some points, nothing that would bring them any harm in the long term, nothing that deserved this darkness. Merlin knows they were used to losing points.
"I'll get you back for this!" He shouted. He thought he did, at least. He felt his brain form the words, his mouth open, his tongue and teeth working, but no sound. Just silence.
But then, a moment later - the retort reverberated around the strange, stretched space.
He hoped that this wasn't some sort of existential crisis, brought on by the humiliation of being shoved into some ornate cabinet by some ginger people. Or a strange dream that impossibly featured the Weasley twins.
"Will that be all, Mr Avery?"
Montague stretched his hand out, into the darkness. There was seemingly no end to this strange cage he found himself in, but the voice must have come from somewhere - and he recognised the ding of a bell, and the sound of a cashier's till... but then the school bell was also ringing, and he could hear thousands and thousands of students' feet trampling along the corridor, and their meaningless chatter.
This was definitely some sort of existential crisis, he reasoned. He was questioning the very foundations of his life; why girls didn't seem to like him, why Potions was so difficult, whether he wrote to his mother too much. The merging of worlds, the distance between thought and movement, between judgement and action.
This was definitely a metaphor for his mortality, he deduced. Or something to do with freedom. That was it. He was free but also restricted; unencumbered, but impeded. He was destined to mundane work, mundane love, mundane life - just like everyone else. Why me? Montague pondered, lodged but also not in this dark space. He needed to reveal the psychological repression of his awareness of his own personal mortality. What is the purpose of existence? The meaning of life?
Montague wouldn't understand, of course, he never would. If he couldn't grasp summoning charms, he wouldn't grasp this.