The Doctor was already descending the exterior stairs, two at a time. Rose struggled to catch up to him.
"Me? Why would they want me?"
"I don't know," he replied, glancing back over his shoulder. "I'm sure when we find them they'll tell us."
"How're we gonna find them?"
"Show me where they were last seen."
"But nobody saw them after that!"
"Exactly."
They had reached the sidewalk, and he was striding along at a rapid pace. "This way, right?" He cocked his head forward.
"Yeah, about a mile." She had reached his side and now half-jogged to keep up. "You think they're still there, by the warehouses?"
"Yep. If no one saw them, they must've ducked inside somewhere."
"What if they went back to their ship? What if they took her back to their planet?"
He shook his head. "Very unlikely. Think about it, Rose. The only connection the Mogronons have to your mother is you. You saw one—nearly bumped into him—twenty-four hours ago. Now he and his pals show up here and take your mother. Somehow they must've traced you an' ended up with her. They won't take her very far away until they find you."
"So they took her knowing that I'd come for her?"
"Probably. Or they may have thought that she had something they wanted—something you gave her."
"But I haven't seen her since I saw them!"
"No, you haven't. But they might not know that."
"So they could've taken her away, back to their planet, thinkin' she had whatever is was they wanted."
"No. Obviously she doesn't have it—for that matter, you probably don't, either."
Rose stopped, huffing slightly, and grabbed his arm. "But if they think I have somethin' they want, an' they took my mum to get it, what're they gonna do when they find out I don't have it?"
He smiled. "Oh, they'll let her an' you go—I think."
"You think?"
"Well, they do have tempers, them. But they're also very determined to get what they want. If you don't have it, they'll most likely try to figure out who does and go after them."
He continued walking, Rose trotting along next to him.
"It really is all my fault, then," she said after a few moments. "If anythin' happens to her, if they've hurt her, it's because of me."
"You couldn't have predicted this," the Doctor said with a glance down at her.
"I knew somethin' was wrong."
The Doctor focused his attention ahead without comment. They had nearly reached the block of warehouses. Rose was struggling to keep up with him; while her mind was wide awake, her body was rapidly losing energy. Still, her drive to find her mother was unwavering. She knew that she would keep moving, keep searching, keep finding the necessary vigor until it was over.
"Okay," the Doctor said, looking around. "This is where they were last seen, right?"
Rose nodded, trying to even out her breathing. She had been gulping at the air and it had left her slightly dizzy. For an instant the cement beneath her feet seemed to rock, and she moved to the side to steady herself.
"You all right?" the Time Lord asked, sparing her a questioning glance.
"Yeah, fine."
But as his eyes moved over her, he could see that she was exhausted. Her eyes were swollen, and her skin was pale, all color drained from her usually rosy cheeks. The knee of her jeans was torn and smeared with blood. He wondered when that had happened.
"So you said you thought they were around here," she was saying, obviously drawing on her emotions to fuel a second wind. "Tell me where."
The Doctor continued his perusal of the area, squinting in concentration as he studied each building in turn.
"No one remembers seeing them past here," Rose said. "They must've left the area—"
"Nope, that's not how they operate. The fact that no one can remember them shows that he made an extra effort here to erase all memories of him and your mum. He thought that would cover up his trail."
"But why would he come out here? If he thought Mum had something he wanted, why wouldn't he keep her at the flat?"
"I think he looked around there enough to know that it wasn't there."
"So he dragged her here? That doesn't make any sense!"
"It does if she told him to come here."
"Why would she—" Rose paused and took a breath. "She was trying to lead him away in case I came back."
The Doctor nodded and said soberly, "Yeah."
"She wanted to keep me safe," Rose murmured. Unexpectedly, she grabbed the Doctor's arm with more energy than he thought she possessed. "We have to find her—now."
The Doctor had removed his sonic screwdriver and was aiming it at the warehouses one by one. After a few moments he switched it off and pointed at one of the buildings. "I'm picking up human heat patterns in there. It looks like one or two bodies."
"It could be workers," Rose said, trying to remain calm though her heart was beating anxiously.
"Maybe, but look around. There's no one here now. They must've gone home for the day."
Rose began to hurry toward the warehouse, but he took her arm. "Wait a minute. We can't just go charging in there. Mogronons don't fancy surprises. We need to be quiet an' take our time."
He began walking slowly, keeping Rose's hand in his. Her palm was clammy and cool, and he could tell that she was frightened, but she did not falter. As they neared the warehouse, they crept low to the ground, heading toward a dusty window along the side of the building. Rose clambered up onto a crate to peer through the dim glass.
It was dusky inside the warehouse, but she pressed her face to the window, cupping her hands over her eyes. About twenty meters from the window, behind a stack of boxes, she saw a figure lying on the ground. The head was hidden from view, but the arms and legs were bound behind the person's back.
"Mum!" Rose cried, half-stumbling as she leapt off the crate and sprinted toward the door.
The Doctor reached for her, but she slipped out of his grasp. Quickly he stepped up onto the crate to look through the window. His eyes darted over the width of the room. There, running across the floor, was a wire…
"Rose!" he yelled, hurling himself from the crate and running after her, "stop! Don't go in there—"
She turned her head to glance at him. "I see her! She's in here." She was reaching for the handle on the large, metal door.
"No! It could be a trap—"
"I have to get her!" Rose flung open the door and dashed inside.
The Doctor was running, counting the seconds, knowing that she would have precious little time. She had surely triggered the system.
"Get out of there!" he shouted as he neared the open door. He could see her bending down by a prone form. He counted two more seconds, then, as if beyond his volition, his body fell flat on the ground as he cried, "Rose! Get down, behind those boxes, now!"
The blast threw the door from its hinges. It hurtled past him to land just a few meters away. He covered his head instinctively, feeling the burst of heat and already smelling the acrid smoke. The moment the ground stopped shaking he scrabbled to his feet and took a deep breath then hurried inside the warehouse.