The man who Mrs. Simmons had seen, as it turned out, had left an impression around the neighborhood. Rose questioned several people and found that they had noticed a huge man lumbering down the street, escorting a blonde woman. No one had caught more than a glimpse of the pair, however, so Rose did not know if her mother had been forced to accompany the man or not. The condition of the flat, though, left her with a fairly strong opinion on that point.

She found it rather strange, actually, that no one had paid the man more attention. All who had seen him noted his bulk, but no one could recall much else. It was almost as though they hadn't given him a second glance, which was odd considering the initial impact he'd had.

As she continued to question people, Rose moved away from her neighborhood. It seemed that someone on each block had seen a massive male walking with a woman, but that was all anyone could remember. Still, it gave Rose hope that her mother was unharmed. No one recalled seeing the woman in any type of distress. Was it possible, she wondered, that her mother had left with him of her own volition? But if that were the case, why was the flat so messy? Why had Jackie thrown the plant?

Rose had covered nearly two kilometers when she lost the trail. She was in a warehouse district with a just a few half-day workers milling about, and suddenly no one remembered seeing the man or Jackie. Rose questioned a handful of people with the same result. After nearly half an hour, she was feeling a terrible mix of discouragement and despair. She wandered a bit further, past the warehouses and back into a residential area, but she had no better luck.

Several people asked if they could call the police for her, but Rose declined. Every instinct told her that the police would be of no assistance. There was really only one person who could help her, and he had vanished into thin air.

It was time to check for the TARDIS again. Rose ran back through the warehouses and rows of dingy flats, pushing aside her fatigue. However, by the time she rounded the corner and saw the police box perched incongruously in its usual place, she was panting. She increased her pace and only slowed when she had pressed her hand against the door.

"Did you get a new phone?" the Doctor asked offhandedly. He barely glanced up at her from his position at the console.

"Doctor," she choked out, "it's—my mum—she's –" Rose coughed, trying to catch her breath.

The Time Lord finally looked up at her. In an instant he was at her side, taking her arm and guiding her to a chair.

"Sit," he said peremptorily.

She complied, although she was still attempting to tell him what had happened. But the more she attempted to speak, the harder it was to breathe.

"Rose," the Doctor said firmly, "just catch your breath." He crouched before her and placed his hands lightly on her knees. "In… out."

She opened her mouth to try to speak again, but he shushed her. For just a minute she allowed herself to concentrate on breathing.

"My mum's gone," she finally gasped out. "The flat's all turned over, broken pots an' stuff on the floor, an' the neighbors saw her with a man, a really big man, an' people saw them for nearly a mile then I lost them, no one had seen them past that, an'—"

The Doctor took her hand. "Okay. We'll find her."

Rose began to stand, but he kept her hand in his. "Just wait a minute. Let's figure out exactly what happened first. You went to the flat and she wasn't there, but it looked like there'd been a struggle."

She nodded. "Then I asked Mrs. Simmons if she'd heard or seen anything, an' she thought Mum'd had the telly on—she'd heard shouting and thumping—but I'm sure that was her struggling with him."

"Maybe. Did the description match anyone you know?"

Rose shook her head. "No."

The Doctor stood, gently pulling Rose up with him. "All right. Let's go back to her flat and have a look around."

They left the TARDIS and hurried back to the apartment. The door was still open, and the Doctor took a few moments to examine the bolt and the knob. Then he stepped inside, followed closely by Rose. He surveyed the chaos, eyes flicking around the room as his expression darkened.

"He forced her to go," Rose said. "She tried to fight him—"

"Looks that way." He began walking across the room, bending to look more closely at several items. He lifted a shard from the broken pot then tossed it aside.

"Whoever he was, he didn't leave anythin' here."

"Wait a minute," Rose said, digging into her jeans pocket. "I found this by the stairs. S'pose it could belong to anyone, but—" She held out her hand with the button on her palm.

The Doctor took it from her, inspecting it carefully. Rose was surprised when he pulled out the sonic screwdriver and ran it over the button. His frown deepened.

"What is it?" she asked, fear again clenching at her chest.

"It's an alloy—gold, molybdenum, an' a trace of Divurscistine."

"Divurscistine? That's the stuff I bought at the marketplace."

"Yep."

Rose felt herself blanch. "Oh God. That means he's an alien."

"Maybe, maybe not."

Rose snatched the button from his hand. "This isn't from Earth!"

"No. But we don't know for certain that it belongs to the man who took your mother. For that matter, what would an alien want with her?"

"I don't know!" Rose threw up her hands in frustration.

The Doctor grasped her wrist and pulled her right hand down. "What's this?" he asked, touching a dark spot on her palm.

Rose glanced down. "Dunno. It doesn't matter." She began to pull her hand back.

He held her hand firmly. "It might."

"Must've burned myself when I was makin' tea," she said. "But what the hell does that have to do with my mum?"

"Probably nothin', if it happened while you were makin' tea. Looks about twelve hours old. Does that sound right?"

"Yeah, probably." Rose managed to retrieve her hand.

The Doctor had turned to stare out the open door. "You said the neighbor saw the man."

"Yeah."

"Come on, then, let's see what she has to say."

The Time Lord waited next to Rose while she knocked on the door. Mrs. Simmons answered, seeming surprised to find Rose on the other side.

"Rose, love! What're you doin' 'ere?"

"Mrs. Simmons, I'm still lookin' for my mum. This is my friend, an' he wants to hear what you told me."

"What I told you?"

Rose nodded. "A coupla hours ago. About hearin' the telly and seein' the man—"

"I haven't seen your mum in ages. Wish she'd keep her telly down, though."

"Right. Like this mornin'," Rose prompted.

"Oh, remember Annie? She called today, or was it yesterday? She's teachin' wee ones in Edinburgh."

"I know. You told me already."

"I did?" Mrs. Simmons blinked at Rose and pushed her glasses up on her nose.

Rose grabbed the old woman's arm. "Mrs. Simmons, please. Tell us again what you heard an' saw this mornin'."

The Doctor placed his hand on Rose's forearm and pulled it away. "Mrs. Simmons," he said amiably, "Rose is going to make us a cuppa." He hooked his arm through hers and led her to the sofa.

Mrs. Simmons smiled. "She is? What a nice girl! Reminds me of my Annie, she does."

The Doctor tilted his head toward the kitchen, and Rose understood that he wanted her to step out of the room. She complied, but her impatience was growing.

Mrs. Simmons settled on the sofa with the Doctor next to her. He smiled affably and lifted his hand to her temple. For an instant she seemed about to protest, but then he pressed the fingers of his other hand over her forehead, and she closed her eyes.

"Think about this morning," he said softly, leaning close to her ear. "About Jackie."

Mrs. Simmons' eyelids fluttered, but her eyes remained closed. The Doctor closed his eyes, too, his brow furrowing in concentration. Rose watched from the kitchen doorway.

When she saw his expression change to one of anger, she hurried to his side.

"What is it?" she asked.

His eyes shot open. He dropped his hand from the elderly neighbor's temple and held a finger to his lips. Quickly he stood, easing Mrs. Simmons' head back against the cushions before removing his fingers from her forehead. He took Rose's arm and lead her out the door.

"What're you doin'?" she asked.

"I thought she was confused—maybe in the early stages of Alzheimer's—an' she couldn't remember clearly. I just took a peek into her memories."

"You can do that?" Rose asked incredulously, then she added, "What did you see?"

His frown deepened. "Not much."

"So nothin' that helps?"

"Oh, it helps a lot."

"What're you talkin' about?"

The Doctor took her arm gently and looked down at her. She was sure she saw sympathy in his expression, and that was more frightening to her than any other emotion he might have shown.

"Alzheimer's wasn't what was clouding her memories. The image of the man she saw was nearly erased."

"Erased? What d'you mean?"

"It was ephemeral, fading away even as I was seeing it."

"Doctor, I don' understand what you're gettin' at."

"Whatever she saw, it left instructions in her memory to delete itself."

Rose was growing more confused by the instant. "What? How could it leave instructions in her memory?"

"The human brain operates at some level much like a computer. If something isn't specifically saved in memory, it won't be available for access later, at least not consciously. You know that there are computer viruses that can mess with data, right? They enter the system through a piece of mail or even through contact with a web site. Whatever Mrs. Simmons saw was sort of like a virus in a piece of e-mail that she opened. Once it entered her mind, it brought instructions to corrupt the data, to erase it from her memory."

"That doesn't make any sense," Rose began to protest.

"I'm afraid that it does, at least to the Mogronons. They can convey messages to most species' minds simply by having the person look at them. They can make you forget what you saw."

"Why would they want to do that?"

He arched an eyebrow at her. "So that no one remembers them clearly."

Rose pressed her hand to her forehead. "That's why no one could tell me what the man with Mum looked like, isn't it?"

The Doctor nodded. "They weren't supposed to remember."

"So this Mogronon thing has my mum." She swallowed. "An' he doesn't want anyone to remember him. He's some sort of criminal, isn't he?"

"Depends on how you define 'criminal.' Mogronons have a nasty habit of taking what they want at whatever price they feel is fair to them. In their view, they aren't stealing, but in the view of most everyone else they are."

"Do you know what they look like?"

"Yeah, I've seen them a few times, an' their memory tricks don't work on me, at least not when I know what they're tryin' to do."

"Are they dangerous? I mean, are they violent or anythin'?"

He seemed hesitant to answer at first. "They're determined. When they want something, they'll get it, an' they aren't concerned about how."

Rose exhaled slowly, her hands clenching into fists at her sides. "So what would they want with my mum?"

The Doctor took her arm again and lead her back inside Jackie's flat.

"Doctor? Tell me why he took her. Please."

"I don't know yet." He closed the door and positioned her against the wall. "Close your eyes, Rose."

"What?"

"Please, Rose, just do it."

She complied, and immediately she felt his fingers against her temples and his thumb press over her skull, just above her hairline. An image flashed through her mind.

"Concentrate on it, Rose," he way saying. "Look at it."

Rose tried to focus, but it was difficult; her thoughts centered on Jackie.

"Come on, Rose. You have to concentrate—it's the only way to help your mum."

Rose forced herself to center on the image as it flickered across her consciousness. She saw a hulking figure with a flat face and short, wiry hair. His small, narrow eyes were flecked with gold.

Suddenly the Doctor's hands were on her cheeks, and his face was very close to hers.

"Have you ever seen anyone like him before?" he asked.

"Yeah," she replied slowly. "I have."

"Where?"

"At the marketplace, just after I got the Divursticine. He nearly bowled me over."

"He was by the vendors' stall?"

She nodded. "I think he was lookin' for them, but they'd all disappeared."

"Damn." His hands dropped to his sides as his expression darkened.

"I don't understand," Rose began, her frustration and fear growing. "Do you think it's the same bloke I saw there? That he's here now?"

The Doctor responded with a curt nod. "Mogronons usually avoid Earth. Terran humans' brains aren't quite as receptive to their manipulation as other species', an' they don't much like the gravity here; bit off for them, makes it just that much harder to move about quickly, as if they didn't have enough trouble with that already. Just goes to show you what inbreeding can do—nasty effects on neuromuscular development. Too much bulk an' not enough flexibility—"

Rose grabbed his arm. "Doctor! I don't care about any of that. Just tell me what's going on."

He looked down at her soberly. "They wouldn't be here if they didn't think it was important. I doubt it's a coincidence that you saw one of them less than twenty-four hours ago."

"So this is somehow connected to me?"

"Yeah, probably."

"But how? I didn't do anythin'—"

"Probably not, but they obviously think you did."

"You keep sayin' 'they.' You think there's more than one?"

He nodded. "They always travel in threes. Takes three to fly their ship."

"So where're the other two?"

"Probably wherever the one who took your mother is." He turned to walk out the door.

"Wait a minute!" Rose protested. "What would they want with her?"

He spun back around to stare at her. "You, Rose. They want you."