A/N: This is an AU story where Sarah Jane dies early within the first series and Luke now travels with the Doctor and Donna. Sarah Jane's death is offscreen.

Luke Smith burst into the house, excited to tell Sarah Jane about his day; today had been a good day. For once he had not made any social mistakes and he had been invited to his first birthday party (that was more because of Clyde's slight interference, although Luke didn't know that). He went into the kitchen, where he knew Sarah Jane would normally be waiting for him with tea, eager to hear about his day. But the kitchen was empty. No Sarah Jane. No after school tea made-although he should have realised that straight away from the absent smell of smoke. He felt a small twinge of unease, and he figured-hoped-she was up in the attic. He rushed off and found himself running up the stairs two steps at a time at a time.

"Mum? Mum!" he cried, bursting into the attic. But it was empty. No Sarah Jane, just silence.

"Mr. Smith, I need you." Luke faced the back wall, and after a few moments of impatient waiting the massive computer slid out of the wall.

"Luke. How may I help you?" The pleasant, soothing voice asked.

"Where's Mum? I can't find her," Luke said, his voice worried. There could be a million reasons why she wasn't there, she was a journalist, after all. Maybe a story had suddenly come up, or even something alien. Luke knew that.

So why was he so afraid?

"Sarah Jane is investigating some alien activities at a warehouse. She left you a note on the table."

Luke looked over at the table; sure enough, there was a small note on it that he hadn't spotted in his frenzy. Upon inspection, it read:

Luke,

I went to investigate some alien activity down at a warehouse.

There are some leftovers in the fridge, just microwave it if I'm not back for dinner.

Mum x

Luke felt a brief feeling of relief, before the feeling of unease returned, partnered with a sickening feeling. He wasn't sure why. Perhaps it was because he'd felt what it would be like if she had vanished, and didn't want it to ever happen again. He knew he wouldn't be at ease until Sarah-Jane had returned.

Dinner time came and went without Sarah-Jane coming back. Luke had waited and waiting for the sound of the door opening or a car pulling into the drive-but the house remained quiet, and the driveway empty. As he checked the driveway for the third time, his heart beginning to pound in his chest, his eyes wandered to Maria's house. He couldn't stand having nothing to do but wait and be worried, and always felt safer with Maria. So, running to the phone, he called her.

"So, Sarah Jane is still gone. Have you tried phoning her?" Maria asked him anxiously. They were sitting on the sofa in the living room, Maria having gotten to his house in what must have been record time.

"Her mobile is off," Luke said. He glanced out of the window at the orange and rose tinted sky. Maria followed his gaze, fear flickering across her face before her expression returned to normal. But not quickly enough for Luke not to spot it. He clenched his hands, and looked to her, expecting her to say or do something to make it better.

"Do you want to come over to my house and spend the night? I'm sure Dad wouldn't mind," Maria offered after a moment's thought. Luke felt a leap of fear at the thought of Sarah-Jane being gone all night, followed by a rush of anxiety at the fact that Maria seemed to think she could be, and looked as nervous as he did.

Luke thought about it for a minute. He would hate being by himself in the big, empty house in the dark. But then he shook his head. "No, she might come home."

"Okay… call me tomorrow," Maria said, then paused. "Are you sure? It's really no problem, we have an airbed, you could sleep in my room."

"No, thank you," Luke replied quietly, resisting the temptation to say yes. "I want to be here when she comes home."

"Yeah," Maria said, nodding. She took his hand, and he felt his heart lift slightly. "It'll be OK. She'll come home, she's probably just held up." Luke managed a thin smile.

"Yeah. You're probably right."

Maria stayed for as long as she could, until the sky had darkened outside. When she left, Luke waved goodbye ruefully from his driveway, watching her run across the street to where Alan was waiting in the welcoming glow of the house's front doorway. He saw Luke and held up a hand by way of greeting, then stepped aside to let Maria inside, closing the door behind them. Luke turned and headed back into the house, his feeling of loneliness and worry ten times worse now she had gone.

He stayed up as late as possible, staring out of the living room window, waiting for her, until his eyes were too heavy to keep open, and before long he had fallen asleep on the sofa into an unsettled sleep.

When Luke drifted awake the next morning, his mind foggy. Then he remembered, and bolted upright. The sky outside the window was bright and birds chirped piercingly. She must be back by now, she had to be.

He got up and rushed up the stairs and to Sarah-Jane's room. He slowed and stopped at the door, hesitating before he reached out and turned the handle. He was met with the familiar scent of her light perfume, and froze as he saw the still open curtains and untouched, cold looking bedding.

In desperation, Luke darted to check the attic, and wasn't surprised when there was still a lack of Sarah-Jane. He felt an overwhelming feeling of panic rise within him, and wondered if he was going to have a panic attack. He didn't particularly care.

"Mr. Smith. I need you!"

Mr. Smith came out with his usual fanfare that seemed inappropriate under the circumstances.

"Mr. Smith, Mum's still not home," Luke burst out in a hurry. "Could you look for her on security cameras or something? Could you track her phone?"

"…There is a report on the news," Mr. Smith told him after a few seconds' pause.

"About…about what?" Luke asked, a chill creeping up his spine. "Mum?"

"Yes."

"Put it up, please," Luke requested, feeling sick as he thought of why she would be on the news. The news channel came up on Mr. Smith's screen, and a female reporter stood in front of a burning warehouse, a serious expression on her face.

"…This is the scene where the warehouse exploded around midnight. One body was found close to the blast, believed to be that of local journalist, Sarah -Jane Smith. Authorities still unsure as to what started the explosion…"

Luke stood there, struck dumb with horror, then slowly sank down onto the attic floor. Mum was dead. He didn't want to believe it. His head told him it was true, but his heart refused to believe it and he didn't want to believe it.

The doorbell rang out downstairs, and even though he knew it was probably Maria, Luke ignored it-he didn't want to talk to or see anyone. He didn't think he could speak. He stood up and went down to Sarah Jane's room as though in a trance, where he curled up on Sarah Jane's bed. He reached for the nearby stuffed owl, holding it tight in his arms. He didn't want Sarah Jane to be dead…he was alone. He didn't be want to be alone. He didn't want to be without her.

The hours slid by; morning turned to midmorning, which turned into afternoon. The phone rang continuously, but still Luke did not move from the bed. He hadn't cried- he was too numb. He knew what death was in the scientific sense, but to have someone he loved die made him feel weird-his chest hurt, but he also felt oddly senseless, like he was drowning, and he didn't like or understand that feeling. He had never experienced it in his short life, and wished he never had.

He only knew one thing: he wanted Mum. The need was a throbbing ache, the only thought in his head, reverberating over and over again. But Mum was dead, and he didn't know what was going to happen to him.

Eventually, he sat up and went upstairs to the attic, the owl still in his arms, having formed some kind of strange attachment to it under the circumstances.

Mr. Smith was still out, monitoring news stories that Luke couldn't stand to look at.

"Mum's dead, Mr. Smith," Luke said dully. "…I don't know what to do."

"I will contact the Doctor. He will need to know, Sarah Jane was his friend," Mr. Smith said, a hint of sympathy in his voice. Luke wondered vaguely if he had the ability to mourn, but didn't ask, his thoughts turning to something-someone-else.

The Doctor. Mum talked about him a lot-she actually had pictures of him, a man with curly hair and ridiculously long scarf.

Luke curled up on the sofa while Mr. Smith made the call: Luke recalled that Sarah-Jane had gotten the number from a woman called Martha. A few minutes later, he heard the unmistakable sounds of temporal engines, and a blue police box materialized in the attic. The door opened with a creek, and a young man in a blue suit, trench coat and red trainers stepped out.

Luke sat up and looked at the man in confusion-was this the Doctor? He looked nothing like the pictures Mum had on her wall.

The Doctor looked at Luke with mirroring confusion, seemingly very bemused. "I must have gotten the wrong place. I…I got a call that Sarah-Jane was dead. Must have been wrong…she's not. Can't be." He was about to step back into the TARDIS, when Luke jumped up, suddenly wanting this strange man to stay with him.

"No, wait! Mum...Sarah-Jane, she is...she's dead."

The Doctor turned around, pain on his expression that was quickly masked expertly. "And you are…?"

"Luke Smith, Sarah Jane is…was my Mum." Luke's voice caught on that last word.

"Sarah Jane never told me she had kids." The Doctor squinted at him, and Luke frowned. "Hang on." He pulled out his screwdriver, running it over Luke. He checked the readings. "Ah, brilliant! You're very brilliant Luke ." He grinned. Luke didn't know if he meant to sound patronising or if that was a poor attempt to cheer him up. Maybe he actually thought he was brilliant, although Luke didn't really see why. He was acting very strangely for someone who's friend had died.

"Oi! Space boy, what's the meaning of this?" A ginger haired woman stepped out of the TARDIS. The Doctor turned to her.

"Donna Noble, I'd like you to meet the son of…a recently deceased friend of mine. He's called Luke Smith. My sonic says he was grown. By Bane, but he's completely human. A genetically engineered child."

"Yes, but what are we doing here?" Donna asked, seemingly uninterested.

"Sarah-Jane's gone and Luke has nowhere to go, so he's going to be coming with us," he replied simply. "Luke, go pack a bag."

The Doctor thought he would contact Luke's school and tell them something or other about why he had vanished. It was the least he could do. He could tell Luke was clever and had a lot of potential as a companion, and if he was left alone he'd end up in a children's home where he would most likely suffer. He was Sarah-Jane's son, and he wouldn't let that happen to him.

He would grieve horribly, but so would the Doctor, even if he hid it. He'd had practice. But they'd get though it together.

Next: The Sontaran Stratagem, where Luke meets Martha Jones and a boy named Luke Rattigan…