I don't own Fringe or it's characters. Enjoy!

OLIVIA DUNHAM'S APARTMENT

Olivia stared up at the ceiling of her bedroom. It was 4 in the morning, or at least it had been the last time she looked at the clock on her nightstand. The lamp next to the clock was on as it had been all night, as it had been ever since she'd got back from Over There. The darkness of that cell had been all the darkness she'd ever be able to stomach, so here she was, lying under her covers in the dead of night, examining in minute detail every inch of her ceiling.

Broyles had signed her off for as long as she needed, once she'd returned, and as the days had drawn into weeks, she'd slowly been able to put her life back together, explaining carefully to Rachel and Ella how the impostor living in her apartment wasn't her. It took them a while to understand, but they had now stopped looking at her with a mix of pity and fear, which had been the hardest thing to bear. Now that they were treating her like an aunt and sister again, it had become easier and everything else had started to get better. Well, nearly everything.

She thought about Walter – He had been overjoyed to see her, putting together the plan to rescue her and send the impostor back to her universe, his tortured mind hiding an intellect that his other universe alternate couldn't match. Seeing the cruelty and malevolence of The Secretary made her appreciate this world's Walter more. Thanks to his actions when she was a child, she was not sure she would ever really trust Walter, but he couldn't hide his tears of joy at seeing her again, nor could she hide hers at seeing him. Astrid was Astrid, and her stoicism was about the only thing that had anchored her in the hours and days immediately after her return. In the weeks afterwards, she and Astrid had become much closer, not least because Walter had told her that Astrid had been the one who had lured her impostor into the trap that sent her back to her world.

She turned over in bed and stared at the clock. 4:12 Am. The cell had screwed up her sleep patterns and the FBI shrink had told her that it might be months before she was sleeping properly again. She sighed and thought about getting up when the phone rang. She picked it up.

"Dunham."

"Agent Dunham." It was Broyles. "Ready to come back to work?"

"God, yes Sir!" She thought she detected a low chuckle on the other end of the line.

"Good. Pack a bag. A train on the Los Angeles subway has derailed in…unusual circumstances. Take Peter and Walter." She paused.

"Of course Sir." There was a long silence. "Is there anything else, Sir?"

"Are you sure you're ready, Olivia?" She rubbed her eyes.

"I was ready two weeks ago, Sir. I was never any good at sitting around. I'm fine." Another silence.

"There's an 8am flight out of Logan. Pick the tickets up at the desk. I'll meet you out there."

She put the phone down and smiled. It had been too long, and the thought of working cases again seemed like exactly what she needed. Only one part of the conversation had wrinkled her brow.

Peter.

NORTH HOLLYWOOD STATION – LOS ANGELES SUBWAY.

The scene was one of almost unimaginable damage and destruction. Temporary arc lights were illuminating the remains of North Hollywood Subway Station and the remnants of the train were compressed and crushed into the remains of the station. The air was full of dust and LAPD, NTSB and local FBI officers running about in the semi-darkness. The NTSB and LAPD officers at the top of the station entrance had handed them all a mask, though Walter had refused his with a cheery "No need officer, my lungs are already damaged by the marijuana I regularly smoke". Peter had ushered him passed the policemen with a cheery "He's a real joker this one!" and Astrid had reminded him about the conversation they'd had about thinking before speaking. Watching the mini farce play out as if nothing had happened made Olivia smile, then she felt a prickle behind her eyes as she remembered how close she had come to losing them all. She quickly blinked away the tears before they had time to form as the descended into the dusty, sodium lit gloom.

The flight had been painfully awkward. For once, it hadn't been Walter who had caused the problems, he's slept most of the flight, ipod headphones clamped to his ears. It had been Peter. They'd had one awkward conversation since she'd been back, and neither had been keen to repeat the experience. His had been the first face she'd seen when she came to after she'd returned. He was holding her hand and he'd cried and kissed her when she came to. He'd spent days in the hospital with her, talking aimlessly about Walter, Fringe Division, the things she'd missed out on here in her world while she was away. He'd tried to get her to talk about her ordeal, about what the alternate Walter had done to her, but she'd been unwilling to discuss it.. Not just because the experience was still so painful, but because she knew that if she told him the truth, He'd go back to that other place and make Walter pay. It was bad enough that he'd risked it all by going back to rescue her, but a mission of revenge was pointless and placed their world at risk.

The awkward conversation had come when she'd found out about the Impostor. She hadn't asked Peter how long it took him to work out it wasn't her because she was terrified to hear the answer. On the other side, in his apartment, stood over the desk with the schematics to the infernal weapon alternate Walter had designed, his son a central component, she'd bared her soul to him, she'd told him that he belonged with her. The possibility that he might have thought the impostor was her, that he had held her hand, kissed her, slept with her, told her things that he should have told Olivia was too much for her to comprehend. She had raised it once and Peter had told her not to worry about it, that she was home, safe, with him but he had looked uncomfortable. She had let it drop and yet her mind couldn't censor the images replaying there, of them both. Together. So she did what she always did to protect herself, she pushed him away. Peter had put it down to her state, Post-Traumatic Stress or something, and he'd left it alone, but he had tried to talk to her about it on the flight, and she had put him down as gently as she could and then pretended to sleep for the rest of the flight. She had no idea how long she'd be able to keep up the distance between them, but she felt betrayed and even though she knew it wasn't Peter's fault, she couldn't help herself.

"Good to see you Agent Durham." Broyles pulled Olivia from her self-reflection. She looked at him.

"How did you get here before us?"

"Took an earlier flight. This is Andrew Kidd from NTSB." He introduced her to a short balding man in a cheap brown suit, who shook her hand purposefully.

"I'm Agent Dunham, FBI. This is Walter and Peter Bishop and Astrid Farnsworth. How many died?" They started to walk towards the front of the wreckage.

" Five. It was an early train and this was the last stop. We lost the driver, two passengers and two on the station platform. Five hours later and it would have been catastrophic," They stopped by the front of the train, which had ridden up onto the platform and flipped onto its side, so that the bottom of the train was facing them. "This is why you're here." He pointed to the wheels, or rather the axles where the wheels should have been attached. Every wheel on the front carriage of the train was missing. "We figure the train derailed at the point the wheels were lost. Problem is, we can't find them."

Broyles blinked.

"What do you mean? They're lost in the tunnels somewhere?"

"No. We've searched the tunnels for three hundred yards, there's nothing we can see that is, or was a railway carriage wheel. These things are four feet across and weigh half a tonne each and we can't find a scrap of metal that looks like a wheel or part of a wheel. It's like the damn train floated here."

Olivia pointed her torch at the axle ends where the wheels should have been. "Were they removed? Sheared off further down the line and momentum carried the train this far?"

Walter was stood behind her and staring intently at the ends of the axles running a finger over the metal, pulled it away and sniffed at it enthusiastically.

"I don't believe so Agent Durham. It's smooth, with no evidence of fatigue or deliberate damage. There are no rough edges. It looks like it was weathered off."

"How can that be?" The NTSB Officer looked at Walter. "This train was serviced yesterday. This was its first run of the day, and you're saying the wheels were weathered off between LAX and North Hollywood? This is titanium alloy we're talking about, it would take ten thousand years for these to weather away." They all stared at the train wreckage.

"Ten thousand years of weather damage confined within a half hour train journey – sounds like a Fringe Division case to me." Broyles said with the slightest smile. Olivia looked at him as her phone rang. She snapped it open and listened for a second.

"OK, we'll be there."

"What is it?" Peter looked at her.

"Second crime scene, someone in the Subway Train maintenance Depot found a body. I'll go with Peter." Walter was still staring at the axle.

"I need these transported back to my lab." Olivia and Peter left as Broyles began the usual refereeing job between Walter and the NTSB officer. She snatched a sideways look at Peter, who was smiling his normal 'I'm glad I'm not involved in that conversation' grin. She loved that smile and seeing it on his face, her heart ached.