Is anyone else pretending last night's episode didn't happen? I just thought it was such a rubbish ending... Anyway, I'm sorry if any of this sounds like it is from the show. It's not, I promise, I wrote this before the episode!

The working title for this was 'Iain Goes Psycho', so, you have been warned. I don't think it's out of character because, as rivernymph99 said, PTSD can make people do crazy things, so, urm, enjoy this?

The unavoidable bouquet, cuff links and a suit, even a dress. This day was a little out of the ordinary. As they made their way to the steps of the registry office, jokily arm in arm, even people who didn't know them could tell that Sam and Tom were going to something more special than work. They were smiling and laughing, but in truth, Sam was feeling more nervous than happy. She was happy, but she felt guilty. The sort of overwhelming guilt that eats away at you until it consumes you so entirely that you do something completely stupid. Sam knew all about that, and she wasn't going to let it happen here. Her hands began to sweat slightly, and her blood seemed to flow faster as she thought about telling Tom, considered his reaction. She had to work to stop herself balking and just running as fast as she could, wherever. Although to be honest, there wasn't much chance of them actually getting married once she had told him, so maybe running was the best option.

She wasn't quite sure when she was going to tell him; it was only fair to tell him before they signed the paper, but she just wasn't ready. She knew how he'd take it, and it made her regret it more than anything. They had reached the doors now.
"Ready?" Tom grinned. Slipping out of her arm and taking her hand, he pulled her up the steps and through the doors.
"Um, no." It came out in a rush. "No, To-"
He ignored her protests, putting them down to last-second nerve, she guessed. She still had his hand though, and she tugged him back in the foyer of the registry office.
"Tom, wait," her voice broke hopelessly.
"Come on, we're going to be late," he chuckling, but his voice was beginning to falter. "Sam?" He couldn't fail to register her tone. This hurt her so much, and just thinking about it made her throat tighten. She was only waiting for the tears now. Tom didn't look so happy anymore either.
She shook her head. "This isn't fair on you, Tom," she said.
"What's not fair, Sam?"
"I've made... A... A mistake," she said carefully.
"What? What, you don't want to get married? What mistake?"
"No, I do. But you won't in a minute," she muttered.
"Well, what is it then," he jumped in.
"Just let me talk," she paused. "I... kissed Iain." There. It was done. She turned to go, hiding the tears that had finally slipped out silently, but he could see the way her body was tense and about to shake.
"When?"
She spun around to face him, but he had turned away now, carefully examining the corner of the small, empty foyer. She couldn't see his reaction; still, she could hear the anger, the hurt.
"The other night. Sunday. After we argued. When I didn't come home," she tried to level her voice.
"I knew it!" he exploded this time, and it was the most enraged she had seen him for a long time.
"It wasn't like that." Try as she might, her fight against the sobs was useless, and her voice lowered.
"Oh yeah? You know, I knew, the minute he turned up here that this would happen," Tom said, the last part more to the walls than to her.
"It meant nothing! I didn't mean for it to happen. I wasn't thinking, we were drunk, it just... Happened."
He said nothing. "Tom, please, you have to believe me, I just want to be with you."
"Then why would you kiss him?"
"I told you. I don't know. But I wish, so badly, that I hadn't. It just made me realise how much I love you, how much I need you," she said desperately. Did he not understand how hard this was for her, to tell him these things. Before, these things had gone unsaid, but they both knew they were there. She felt like she was having to prove herself now. And yet, she still wanted him. She was stupid. Useless. She couldn't do anything right anymore. Tom was still wordless, and she couldn't see his face to gage his thoughts, but to her, his silence meant the worst.
"I'm sorry," she whispered. It was harder to leave on this note, but he obviously didn't want her. She opened the door.
"Sam. Wait."

Sam looked up from the steps, turned her head towards him. Tom was still facing the corner, a hand lifted to his forehead. It was like he hadn't said anything. But he had, she was sure of it.
"I don't want this to be it," he said slowly. "I came here to get married, so..." he began grinned. She was standing behind the door, but she was about to run - clichéd, but she couldn't help herself - to him, when he opened his mouth to shout, and someone snatched her from behind.
A hand around her neck, cold metal pressed to her head, familiar heavy, rushed breathing.
"Iain?" Sam cried. Tom made for them, and as she heard a click, she realised a gun was pressed to her temple.
"Stop, or I'll pull the trigger," Iain said, and he was almost calm. Tom halted. Sam tried to twist herself out of his grip, but her counteracted her self-defence; they had been taught the same skills.
"What are you doing, Iain?" Tom snarled. Sam tried to tell him to shut up with her eyes, and he seemed to get the message.
"If I can't have her, neither can you," Iain growled.
"Iain, just stop, please," pleaded Sam. "I'm sorry, if I made you think I still wanted you, but I don't. It's not the same as it was before, and I think you know that. Tom and I, we're happy, we're getting married. Can't you accept that and let me go?" She looked right to the corner of her eye, trying to see his face.
And then there was nothing. For a long time, it seemed, that there was nobody in that small room, except three motionless figures, one standing apart from the others, but no sound, no movement. And then it stopped, the present flooded back, and Iain crumpled. He let Sam go and fell to the floor, shaking. She took the gun carefully from him, putting the safety catch on.
She and Tom were quiet. There was nothing to say, not in those first few moments.
"I think he needs help," Sam said. "I think it's post-traumatic stress disorder." She explained their visit to Birmingham.

"What about the wedding?" Sam asked quietly, after they had taken Iain to the hospital.

"We've probably missed our chance now. We'll book it again though, yeah?" Tom smiled tentatively.

"I'm sorry, for everything I've done, especially last week," Sam paused. "But I really, really love you, so much, so thank you for the second chance," she couldn't really tell him exactly what it meant to her, so she grabbed his face and kissed him hard, and once his surprised expression had diffused, he relaxed into her, kissing her back before they got in the car to drive home.

Thanks for reading :)