As the app finished its work, Darren looked around the stone walls of Castle Shepton. He had to admit, the act of travelling -- or 'swapping' as he was coming to think of it -- was a little disappointing in the special effects department. It was like turning the light off in a room, then turning it back on and finding one's self in a different room. If this was TV sci-fi, he was on a Seventies Doctor Who budget rather than Stargate SG1.

He was in what looked like a medieval armoury, packed with halberds and leather breastplates. This time, for the first time, it all made a little more sense. He'd appeared in various places around the castle when he visited and had a pretty good idea where he was going, so he headed for the kitchen.

As he walked, all the possibilities of the situation ran through his mind and he realised how lucky he'd been not to appear in front of Lord Winsome, or in a compromising position with a maid.

Worry weighed heavy on his mind but it was wiped away in a moment when he strode into the kitchen and saw Lizzy standing over her cauldron, stirring with a thoughtful expression on her face.

When he looked at her, everything else became superfluous. It wasn't just her soft features and nervous smile that so arrested his attention -- it wasn't even those gentle curves or the way her cheap clothes swayed when she moved. It was her genuine personality, no thought of pretence or front to mar her reactions.

He was utterly besotted with her, he realised, which might have been why he walked straight into the slap she delivered when he approached. Reeling, it was all he could do to hold his cheek and look at her tear-stained face as he felt his mouth drop open.

"What was that for?"

"Do not attempt to fool me, Marcus. I know it is you in there, hiding behind a facade. Raff saw you -- he saw you change. Whatever witchcraft you are using for this cruel game, I will not fall prey to it again."

"Who the hell is Marcus?" She turned away, refusing to answer him and concentrating on her stew, but things were starting to fall into place. He thought back to what the DVD seller told him once they got discussing. Quid pro quo. "Oh, love, no -- you misunderstand. I think I see what's going on here. I just found out that, when I travel here to see you, I have to swap places with someone from here. It's an immutable law of reality, or something. I don't really travel anywhere, I just take up an already occupied position. This Marcus character must be the person whose place I take, and he takes mine while I'm here."

She stopped stirring but kept her back to him. The tense set of her shoulders told him she was fighting tears.

"I swear to you," he continued. "I have no idea who Marcus is. I'm Darren Denny, and I come from a place where I'm deeply unhappy through a magic app I don't understand but am deeply grateful for. Because when I'm here with you, Lizzy, the world seems saturated in colour. I want to cook with you until we wither away, to hold you till we share our last breaths, to be your man -- if you'll have me --and dedicate the rest of my life to making you happy."

"The way you kiss me," she whispered. "The tender caress of your hand. These things are your own, and have never put me in mind of Marcus -- a vile man by any standard." She turned and stared into his face. "Can it be true, this thing I hoped so hard was real -- are you really here for me, forever?"

Darren realised he'd been uncertain up until this point, genuinely torn over what he wanted to do.

The Chinese man's parting words came to him on the wings of haunted memory.

"You must make a choice -- a permanent one. Every time you switch places, your hold loosens. If you don't pick one to stay in, you will be unable to hold on to either."

"What happens then, if I don't have a reservation?"

"If you don't have a reservation, you cannot get in."

"What does that mean?"

"Believe me, Mr Denny -- you don't want to know."

Everything he knew, everything he owned, was in present day London -- friends, colleagues and a successful career he'd spent decades building. But he knew -- right here, right now -- staring into Lizzy's astonishing eyes, the love of his life lived in Shepton Castle long before he was born. Really, with that revelation, it didn't feel like there was any decision to make.

"Yes," he answered, the word a bold note of joy on the faintest of breaths.

The moment held for a wonderful eternity, their eyes aligned to the soundtrack of a gently boiling stew.

Then something hard and heavy smacked into his shoulder.

"Traitor!" shouted Raff, brandishing the fire iron he'd just hit Darren with. "Leave her alone, Marcus -- I will not let you harm her!"

"Oh, sweet boy," said Lizzy, stepping between them and snatching the iron. "How brave of you to defend me, but I believe this is Darren. I think I always believed it. This is not Marcus."

"Indeed," added Darren, "if I'm right, when I come here to stay, you'll never have to see Marcus again." Although, I get the feeling my wife knows who he is!

"You aren't staying now?" Her eyes looked as big as he'd ever seen them.

He shook his head. "I have some loose ends to tie up, and I have to collect together some amazing ingredients to bring with me." Excitement was racing through his system so he was almost buzzing.

"I should get on with it, before anything happens to get in the way."

Her hand touched his a moment before her lips. "Stay with me a little while first," she whispered.

They made love in the skullery, perched precariously on the crockery preparation table. For Darren, it was a loving morass of lips and love, passion and tenderness. There was no trickery to Lizzy - no need for gimmicks or quirks or roles. It was honest, and that was something he hadn't felt in too long.

After Raff shouted at them from the main kitchen, they rushed together a meal for Lizzy to present to Lord Winsome, giggling and throwing one another gazes as they went. By the time his phone buzzed, warning him he'd need to leave, Darren was already compiling a mental list of people he needed to talk to, things to buy, and preparations to be made.

There was just time to arrange a nasty surprise for Marcus. Raff showed him back to the armoury and he placed himself crouched over a spiked mace. Unprepared, there was no way Marcus would avoid sitting on it. At Darren's ushering, a giggling Raff fled the room and, hopefully for the last time, Darren headed back to the future.