More than once some ill-meaning magic user had enchanted Camelot residents to become besotted with somebody they really shouldn't be remotely interested in. There had been the imp princess, for example. And the troll incident. Merlin had occasionally wondered whether a side effect of using magic was that the user found themselves with their affections pointing in an entirely unfortunate direction. He usually wondered this after catching himself smiling thinking about some comment Arthur had made over dinner, the way he'd tripped over his boots and admonished Merlin for leaving them there (it was Arthur who'd kicked them off at his bedside), the way his blonde hair had caught the light that evening as he stood at his window, wrapped in sunbeams.

A side effect of using magic, Merlin thought hopelessly. A likely story.

Either way, it came as no real shock when Arthur began behaving strangely. Magic had a habit of creeping into the castle unannounced and unwelcome. The fourth morning in a row Arthur demanded that they go for an early morning ride to pick volumes of flowers on the hillside, Merlin began to suspect magical involvement. When he caught the prince gazing wistfully out his chamber window while he should have been training, he decided he had better look into things.

'It's happened again,' he said to Gaius over dinner, exasperated. 'A love spell or a potion or some inane magical creature, they've enchanted Arthur.'

Gaius raised an eyebrow from across the table. 'How do you know?'

'Trust me, I know that kind of magic when I see it by now. He's besotted. Wistful. He missed sparring this afternoon.'

'Sounds serious,' Gaius reflected, gathering a spoonful of soup from his bowl, 'and why have you not yet acted on your suspicions?'

'I've tried,' Merlin was almost obstinate, but Gaius had a point. 'Nobody new has come into the kingdom, nobody has come to the castle, no-one nearby has any kind of motive.'

'Hum,' said Gaius. 'Perhaps it is some kind of playful magical creature. They have nothing to gain from Arthur's behaviour besides entertainment, after all.'

'Good idea,' said Merlin, demolishing his soup. 'I'll look it up.'

It was easier said than done, however. Every reference in Gaius's books to creatures who meddled with human affection was short, since most entries gave a brief description and then, 'If enchanted, plead with the creature and/or destroy it.' The books gave little instruction on locating the creatures to plead your case and anyway, there was no certainty that it wasn't something else meddling with Arthur's reason.

Meanwhile, Merlin was struggling to get Arthur to his important royal engagements on time. If there was a creature interfering with the prince, then all it could be gaining was Uther's increasing frustration at his son. Merlin supposed he would have found this vaguely amusing if the fallout wasn't so often on him.

Late one afternoon, when Arthur had failed to arrive at dinner and Merlin had been unable to locate him within the castle, Merlin decided to take his chance to search Arthur's chambers for potential creature invasion. He was crawling along the side of the bed peering beneath it, examining some scratches in the dust that could have been pixie footprints, or they could have been an indication of how little he dusted beneath the furniture, when the door opened. Merlin watched Arthur's feet make their way across the room and stop at the table, something rustling from above them. Merlin poked his head over the side of the bed. 'Hello.'

'Merlin!' Arthur was more alarmed than angry, his hand jumped to his hair and he dropped the armful of heather he was adding to an already gratuitous flower arrangement on his table.

'Sorry, just dusting – why weren't you at dinner? Your father's going to lose it if you do that one more time this week, and... you've been off flower picking.' He sighed. 'Right. Arthur, sit down.'

Arthur sat. His willingness to comply was worrying. Merlin crossed the room, dusting off the knees of his trousers, and leant forwards to look into Arthur's face. The afternoon sunlight was trickling across his face, casting a strange light through his eyes – or was that the enchantment, Merlin forced himself to consider, resisting the urge to run a finger along Arthur's sunlit jawline.

There was nothing he could tell from Arthur's face. He'd have to ask him to gain a few more clues.

'Arthur,' he said, seating himself opposite and looking carefully at the abandoned heather clumped on the table, 'I know something's got into you. I don't know what, exactly – but I don't think it's good. I think you – I think – have you been thinking about someone, recently, in a – a different way? Like – have you...' he trailed off, not particularly wanting to finish the sentence. He tore his eyes from the heather and looked up at Arthur.

To his surprise, he was looking back – not affronted, not annoyed – but with a fierce and solid expression of agreement. 'Yes,' he said, 'Yes.'

Oh good. Let's hear all about princess so-and-so from the pixie land of flaberjaroo, thought Merlin. Arthur stood, moved to the window, ran his hand again through his hair. Merlin returned to looking at the heather, frustrated, though he knew he was about to make some progress in his current mystery.

'I – I can't stop thinking about it,' said Arthur, haltingly. 'I just – it seems so right to me, so real – I tried to put it out of my mind, I did.'

Merlin raised his eyebrows. After a number of trouble-causing enchantments, had Arthur learnt to put up something of a fight?

'But I just couldn't stop, and it was so hard to fight it – so I just put myself out of the way, I avoided – things – but I couldn't stop myself thinking. And now – and now – '

'Who is she,' enquired Merlin dully, wanting to reach the crux of the matter before Arthur gushed his way into oblivion.

'She?' Arthur moved away from the window. He was beside Merlin. The servant looked up at the prince, Arthur's hair all aglow in the afternoon sunlight. 'Merlin.'

And before Merlin could produce a response, before he could come up with one small thought other than the glow encasing Arthur's silhouette, Arthur had grabbed his roughly by the shirt. His first, instantaneous thought was of espionage by magical creature – of course, Arthur had been enchanted to attack Merlin, the greatest protection he held, the only person Merlin would fail to hurt to defend himself – but then Arthur's mouth was on his own, and every other thought, every negative inkling, vanished into thin air.

This kiss – this kiss was fierce, and determined, and everything Arthur was – Merlin could taste his lips, feel his heart beating against his own chest, the world was Arthur –

And he shoved him away, pulling the chair between them. The prince stared at him, breathing heavily, his expression so tragic and abandoned that Merlin never knew how he could resist throwing the chair aside and falling on him with an indecent fervour.

But he did.

'Arthur,' he said, licking his lips; they still tasted of him. 'Arthur, you've been bewitched. Something's enchanted you, this – this isn't you.'

'Merlin,' Arthur said, 'Merlin.' He spoke it like it was the only word in his language, a word wrapped up in a desperate need.

'We need to go and see Gaius.'

As it turned it, it was pixies. A troupe from the next kingdom over had been making their way through the lower town, causing general mischief and minor disturbances. They were genial enough when Merlin confronted them, and lifted their charms before buzzing out of town to continue their reign of tomfoolery elsewhere. Merlin had wondered whether he should destroy them before they caused more significant problems, but the memory of Arthur's lips pressing against his own stopped him. He could not in good conscience deprive someone else of that moment with their own Arthur, even if it was all a spell.

The disenchanted Arthur returned with vigour to his usual practices; attending dinner, training, and no longer visiting the hillside. Merlin missed the scent of flowers in Arthur's chamber, but mostly he missed having Arthur close to him, that look on his face... he forced it out of his mind. Arthur hadn't mentioned what had occurred in his bewitched state, and neither of them had given Gaius the details. Either he'd forgotten all about it, or, Merlin thought miserably, he was so hideously embarrassed by the whole affair that he would never voluntarily look at Merlin again.

But just for that one moment, in the sun...

It was several weeks later. Arthur had at least shown no sign of wanting to replace Merlin with another, less embarrassing manservant, but Merlin thought he behaved differently; certainly, he looked at him more thoughtfully. Perhaps he remembered, as Merlin did, that for several seconds into Arthur's moments of madness, Merlin had not pulled away. Perhaps he was wondering what kind of execution his father might put both of them to if he had known. Merlin didn't ask.

It was odd, therefore, when Merlin entered Arthur's chambers one afternoon and found Arthur seated on the windowsill, twirling a sprig of heather in one hand.

'Arthur?'

'Merlin,' he said, standing, 'got you a present.'

He beckoned to his manservant to join him at the window, and held up the sprig before his eyes.

'Er,' said Merlin, reaching uncertainly for the sprig. Arthur twitched it out of his reach.

'I have a question first.'

'Yeah?'

'Yes.' Arthur clasped his hands behind his back, holding tightly to the heather. His gaze slid sideways towards the window. Merlin could see the light causing that same effect on his eyes, soaking up the sunbeams. 'Is it not standard, Merlin, that when someone is addled in the mind, and they – they behave affectionately towards you, you should distance yourself from them?'

The bottom dropped out of Merlin's stomach. 'Yes, sire.'

'You should not, for example, return that – affection?'

'No, sire.' Merlin could feel his cheeks burning. He lowered his eyes to the floor even as Arthur looked at him. He was either going to cry or be fired. Possibly both.

'Good. I just wanted to check that you were aware. Because if you do that to me again, Merlin, I could easily have you hung.'

'Yes – sire.' His eyes were burning now. He turned away, scared the lump in his throat wouldn't hold to the door.

'Where are you going?'

Merlin stopped, facing the door. He took a deep breath. Not talking about what had happened had been so, so much better. So much easier.

'Merlin, I said I'd gotten you a present.'

Merlin turned. Arthur was holding the sprig of heather in an outstretched hand. He was certainly crueller than Merlin had ever thought him. Their fingers brushed together as Merlin reached out and took the heather, and Arthur's hand closed on his wrist.

'What I mean to say, Merlin, is that if you ever take advantage of me like that again, you'll be in trouble. But if you walk out of this room without telling me exactly why you didn't shove me aside the second I – you'll be in even worse trouble.'

The lump in his throat was making it impossible to talk. The words wouldn't have formed anyway. They were his secrets, and Merlin never told his secrets. Never.

'Merlin.' He recognised Arthur's exasperated tone.

'I – it doesn't matter.'

'I think you'll find it does.' Arthur's thumb moved over the skin of his wrist, a gentle motion. A trail of goosebumps fled up Merlin's inner arm.

'Arthur – Arthur, I – ' Arthur's touch and tears that had just been prickling at Merlin's eyes and the scent of the heather between them was making it hard to think. 'I'm sorry, I –'

'Merlin.' For the first time since Arthur had waved the heather under his nose, Merlin met his gaze. 'Don't lie.'

He had never wanted to admit to something more in his life; it was worse than magic, much worse.

His fingers moved as if separate from his mind; his wrist still clasped in Arthur's grip, his hand moved over to Arthur's arm. The heather crunched as he grasped his sleeve.

Arthur stared down at their clasped wrists for several seconds. Several, long, terrifying, hopeful, awful seconds.

Then his free hand was at Merlin's jaw, and it was happening again – Arthur's heart beat against Merlin's chest, Merlin's breath was in his lungs, they were still clasping each other's wrists tightly –

They stopped, but it wasn't a shove; there was no chair in the way. They breathed in each other's air for a moment, their foreheads pressed together. The warmth Arthur radiated, Merlin noted, was much greater than any the afternoon sunlight could provide.

'How long?' asked Arthur, his eyes closed.

'Ages,' said Merlin. It was strange to produce a truth. 'How long for you?'

'I think it had been coming on for a while,' Arthur's mouth twisted into a smirk, 'but I'll admit, those pixies certainly opened my eyes. A bit.'

'Just a bit?'

'Just a bit.'