“I don’t care,” said Cat. He picked up the top mattress and shook it, trying to shake the smell – or the spell – out.

This proved to be a bad mistake. The whole basement became full, almost instantly, of thick, choking, bad-smelling, chaffy dust. They could hardly see one another. What Cat could see of Tonino was alarming. He was bending over coughing and coughing, a terrible hacking cough, with a whooping, choking sound whenever Tonino tried to breathe in. It sounded as if Tonino was choking to death, and it frightened Cat out of what few wits he seemed to have.

He dropped the mattress in a further cloud of dust, snatched up a broom and ran up the stairs in a frenzy of fear and guilt, where he battered on the door with the broom handle. “Help!” he screamed. “Tony’s suffocating! Help!”

Nothing happened. As soon as Cat stopped beating on the door, he could tell from the sort of silence beyond that Master Spiderman was not bothering to listen. He ran down again, into the thick, thick dust, seized the choking Tonino by one elbow and pushed him up the stairs.

“Get up by the door,” he said. “It’s clearer there.” He could hear Tonino choking his way upwards as he himself ran towards the dirty, murky high-up window and slammed the end of the broom handle into it like a spear.

Cat had meant to smash out a pane. But the grimy glass simply splintered into a white star and would not break any further however hard Cat poked at it with the broom. By this time he was coughing almost as wretchedly as Tonino. And angry. Master Spiderman was trying to break their spirits. Well, he was not going to! Cat dragged one of the heavy, splintery work benches under the window and climbed on it.

The window was one of the kind that slides up and down. Standing on the bench brought Cat’s nose level with the rusty old catch that held the two halves shut in the middle. He took hold of the catch and wrenched at it angrily. It came to pieces in his hand, but at least it was not holding the window shut any more. Cat threw the broken pieces down and gripped the dirty frame with both sets of fingers. And pulled. And heaved. And rattled.

“Let me help,” Tonino said hoarsely, climbing up beside Cat, and breathed out hugely because he had been holding his breath as he came across the room.

Cat moved to one side gratefully and they both pulled. To their joy, the top half of the window juddered and slid, making an opening about four inches wide above their heads. Through it, they could just see the bottom of a set of railings, level with the pavement outside, and pairs of feet walking past – feet in old-fashioned sort of shoes with high heels and buckles on the front.

This struck them as strange. So did the way that warm wafts of fresh air came blowing in their faces through the open gap at the same time as clouds of the dust went streaming out. But they did not stop to think about either of these things. It had dawned on both of them that if they could pull the top half of the window right down, they could climb through and get away. They hung by their hands from the top of the window, pulling grimly.