The warehouse disappeared. Forces tore at Donatello, raking his skin, twisting his muscles. He screamed into the light, so bright it was painful. He couldn't breathe against the band of pain across his chest.

Then he was on the ground and his starving lungs gulped in air. But the air burned his throat, filled his lungs with agony. He gasped in another breath, choking, feeling the acid burn on the inside of his mouth, feeling the blood vessels burst in the back of his nose.

A weight landed on him, pinning him down. Strong hands forced a mask over his face. He kicked, struggled against the arms that gripped his, the knee pressing on his chest. His lungs screamed, his throat was on fire.

Two masked faces hovered over him. He lashed out, knocked one of them aside but the one kneeling on his chest caught his arm and slammed it into the ground. Sharp pains tore at his skin. He coughed and a spray of bright red patterned the inside of his mask.

The other mask reappeared in his vision, leaning down until the visors touched. He saw a face, a woman's face, behind the visor. Words came through, muffled but audible through the mask contact.

"Don. Don! It's April! Calm down. We're trying to help you!" The face loomed over him, blue eyes focussed on his. How did she know his name? April? This wasn't April. Where was he? Where were his brothers? He coughed again, felt wetness on his lips.

"Don, please. You're using your air too fast. You've got to calm down."

That penetrated the panic and connected with the cooler, logical part of his brain. No air was bad. He made a conscious effort to slow his breathing. He could hear the rasp and hiss of his breath, and under that the pounding of his heart. The sky above churned in hideous colours, gases mixing and swirling. Dimension X. It must be Dimension X. But how had he got here?

The woman shook him, gently. "Don. We need to move. Are you with me?" A curl of hair fell across her forehead, bright red.

He stared into the blue eyes, managed a small nod. The weight on his chest disappeared. Hands gripped him under the arms and he was hauled to his feet. He staggered against them, reeling and dizzy from the lungful of poison. The tank attached to his mask bumped against his shoulder. They half-dragged, half-carried him across the broken landscape to a van, parked in a clear spot between ruined buildings.

Inside the van they let him collapse on the floor and the world faded for a while. He drifted in and out of consciousness. When he awoke, the woman with the red hair was sitting next to him, supporting him as he lay on his side, her hand resting on his shoulder. He stared at her face. She had said her name was April. That much he remembered.

She saw him watching her and leaned down. "Okay?"

He nodded.

"Another hour and we'll be there. Just hang on."

"Where-" he managed, before another cough tore through him.

"The compound. We'll be safe there."

"No. Where is...here." It hurt to talk, and the blood in his mouth tasted coppery and sharp.

She studied him, gaze roaming across his face. "New York."

"Not...New York." Not this stark, horrible landscape. It couldn't be.

"It is. It's New York in the future." Her hand reached down, fumbled for his fingers, squeezed. The warmth startled him. "It's 2029, Don. You've come forward in time."

Forward? His mind wouldn't process her words properly. "How-?"

"Too hard to explain." Her breath misted the inside of her mask. A bead of condensation trickled down. "But it's the truth. I'll give you the whole story when we can talk without masks."

She sat up, breaking the contact. Donnie lay on the floor of the van, feeling the vibration of their movement, the jolting shudder as they bounced over the rough road. 2029. The number played over in his head, meaningless. He rolled onto his knees, got one leg under him and struggled upright. The woman stood with him, hand held out to assist, but he ignored it and staggered to the narrow windows at the back of the van.

The world peeled away behind them. The horizon was a jagged circle of teeth rising into the sky, empty windows pockmarks of decay. Colours were muted, twisted. No blue sky. No sun. On the collapsed ruins beside the road strange growths pulsed, shocking-bright. Pustules burst, sending clouds of gas into the air, harsh pinks and fluorescent green and dull, smoky grey. Some sort of alien respiration, his scientist mind said. He retreated there, to the unemotional side of his self, away from the stark horror in front of him.

2029. Sixteen years in the future. What had happened to create this landscape? But he knew the answer already. He had seen a world like this before, looking through a Kraang portal. This was Dimension X brought to Earth.

And the woman who had rescued him...no. He turned and found she was watching him. It was hard to see her features from here through the mask, but the blue eyes were visible. April. Older. He leaned on the wall of the van, his hand shaking. It couldn't be. You're dreaming. A nightmare. You got knocked out. But everything was too real, too solid.

Something beeped behind him and he turned around, then realised the noise came from the tank slung over his back. April reached into a locker and pulled out another tank. She gestured him over. When he reached her, she leaned forward to touch her mask to his. "You need to swap tanks. Take a deep breath."

The first deep breath sent him into a spasm of coughing. When he had his breathing under control again he took a more cautious breath, filling his lungs until they ached, fighting the need to cough. April disconnected the tank with quick, sure movements, snapping the new tank into place.

He released his breath, leaned over and coughed until his chest hurt. April put a hand under his elbow as he slid down the wall. He saw her lips move.

He couldn't hear her voice, but he thought she had said I'm sorry, Don.