The kettle whistles cheerily on the hob as I spoon herbs into a stainless steel tea ball. Dropping it into my Grandmother's old teapot, I retrieve the boiled kettle and fill it halfway. I have an electric kettle, used for everyday tea and coffee, but if it's herbs, if it's for healing, I use Nin Grey's willow patterned pot and clunky great kettle. Gripping the cool marble worktop to stop my hands shaking, I take a deep breath and centre myself.

You are entirely out of your mind, I inform myself sternly, watching aromatic steam curl from the spout of the teapot. Goddess, what do I do?!

When no divine answers are forthcoming, I snatch up the cordless phone from by the toaster and press speed dial three for the next best thing. It rings six times before a cheerful, maternal voice answers, worn thin with age and bronchial asthma.

"Hello pet, I had a feeling you'd ring. What's troubling you?"

Nin Grey is Dublin Irish, grey-eyed and flame-haired, although the red is from henna these days. If you placed photos side by side of a young Nin and I, you'd swear we were sisters. I have her grey eyes, and my Mum's wild black hair. I was nearly named Brenna on account of my hair. I take a deep breath that quavers. Nin coughs and I hear her asthma inhaler hiss.

"Nin," I begin. "I'm in it up to my neck."

Unconsciously, I lapse into Gaelic and tell her the tale from the beginning. Feeling the pull, tracing the thread through the ether, the impossibility of Nuada's presence, his terrifying mood swings. Nin listens to it all, occasionally asking questions, but mostly just listening intently.

"Ah, wee girl, you always did have a nose for trouble," she comments, affectionately, as if I was five again and had skinned my knee.

"Nin!" I protest, voice rising. "I've got the Crown Prince of Bethmora prowling around the spare room!"

A pause, during which I can hear her rattling a peppermint against her teeth. Eighty five and she's still got all her own teeth.

"Have you aired the bed?" she asks reasonably.

I think I'm going to explode. I lean on the counter top, kneading the bridge of my nose, and then fish the tea ball from the pot before pouring a cup. Just as I open my mouth to retort, she starts to speak.

"Listen and listen well, dear one," she instructs, enviably calm. "I don't know of anything in this world that can resurrect Gentry gone to stone, but I was visited by a white owl last night. She told me that the scales were tipped by the Royal twins death and that imbalance must be redressed." Nin sighs and I can hear her chest rattling. "You know as well as I that nature is cruel as well as wonderful, and that She abhors a vacuum. The time of the Fey wasn't due to end, but when Nuala stabbed her pretty wee heart, she opened a crack in the world that they've been slipping into and things have been scurrying out of. The BPRD have had a busy few years because of it. There's been tsunami, earthquakes, hurricanes, barren cattle, mass suicides... all because a door opened that wasn't supposed to. The Prince can put it right, but only if he wants to. And that, my pet, is where you come in. He needs to be healed."

I look at the cooling tea and wonder, distractedly, if the fate of the world can be read in the wet leaves. Nin allows me a few seconds to let it all sink in. I hear her unwrap another sweet.

"No pressure then," I joke, faintly. I wonder if I have any brandy left.

"We're people with a foot in both worlds – human and Fey. The line reverts to its origins every thirteen generations. That will help you bridge the void with Nuada."

I'm generation thirteen. I've known it since I was old enough to count. Magic has always come easily to me, too easily sometimes. My connection with the earth is so strong, that if I spend too much time in the city, I get listless and crotchety.

"Nin," I whisper, holding the phone close to my mouth. Nuada is in the guest room upstairs and shouldn't be able to hear me, but I lower my voice anyway. "I'm bloody scared. His Royal Highness isn't playing with a full deck. What if he decides to go on a rampage? There's not snowball in hell's chance I can stop him. If I tell the BPRD, they'll lock him in maximum security containment till doomsday."

Nin Grey is quiet. We both know this isn't something where the outcome is certain. We both know I'll have to tread very carefully. I know it's something I just have to do, whether I like it or not.

"You'll find a way, pet," she assures me. "I'm just on the end of the phone. Now, take him his tea and let an old lady get back to her Sudoku."

"I love you, Nin," I say, trying to swallow the lump in my throat.

She tells me she loves me too, with a catch in her voice, and hangs up. Numbly, I pick up the oversize blue mug, patter across the quarry-tiled kitchen floor and push open the door to the hallway. My house is Georgian, dating back to the eighteen hundreds, three storeys of hand-me-down antique furniture, books and occult paraphernalia. Trinketry and trash, as my rather sniffy great Auntie Mabs calls it.

Nuada is sat in the dark on the stairs, chin in his hand, peering through the spindles. He has soaked in the bath and changed into a clean black t-shirt and wash-faded denims, both relics of boyfriends past. His feet are bare and he has tied back his hair with an old blue velvet ribbon I recognise as coming from the button box in my study. So the Prince likes to poke around in drawers. He is still wearing his gauntlets and his lance rests across his knees like a favoured pet. Mysteriously, it has somehow retracted to about a foot in length, scant inches of wood between the blade and the engraved haft.

Accepting the offered cup without comment, he stares at the oak Ogham shield above the hall door lintel. It's a carved house protection, an invocation to the Goddess Brigid. The Prince sniffs the cup contents suspiciously, nose wrinkling. Apparently satisfied I'm not trying to poison him, he sips the hot brew.

"Can you read that?" he asks, gesturing with the steaming mug.

Sensing I'm being tested, I push my hair behind my ear and turn to the shield. "Hail to thee, Lady of the Sacred Flame, daughter of the mighty Dagda, whose eyes see all. Cast your fiery arrows against those who would disturb the peace of my home and my heart."

He snorts quietly and drinks more tea. "Fortunate are those who have peace to disturb."

Expression darkening, his gaze becomes distant, troubled. The Prince is brooding, but at least he is calm and reasonable. For a man who's been dead, turned to stone and shattered to pieces for three years, he looks so alive. A pulse beats steadily in his white neck, he exudes vitality and strength. Elbows resting on his thighs, his arms and shoulders are muscular from countless hours practising with his lance. He looks like what he is; a battle-hardened soldier, scarred, self-contained, deadly. His hair shines, streaked sodium orange by the streetlight filtering in from outside. I look at his hands, with their pewter nails, now clean of the grime caught beneath them. Goddess help me, he's beautiful. I'm no impressionable teenager, far from it. I've seen and done too much to have my head turned by any preternatural bad boy, but I can't help myself, he fascinates me. Sensing my scrutiny, Nuada turns his amber eyes toward me.

"Why do you stare at me?"

I shrug, increasingly my mental shielding. "I've never seen a full blood elf before," I answer, truthfully. "Besides, your Highness, you're looking remarkably spry for a dead man, even if that t-shirt is a size too small."

On his feet, aloof and irritated, his shoulders square threateningly. "You mock me! Is this the treatment I should expect? Will you telephone the red demon now?"

Glaring back at him, I fold my arms, uncowed. Nobody shouts at me in my own home, not colleagues, not family, not even Fey Royalty. "One, I'm not mocking. Two, you are a guest in my house and will treat me with the appropriate respect. Three, if I had any bloody intention of ringing the BPRD, you'd already be shackled and halfway to fucking Outer Mongolia by now!"

The cut crystal vase on the hall window ledge emits a low, oboe note and I realise I have roared. That's a fiery Celtic temper for you. I have my Dad to thank for that particular character trait, and my extensive vocabulary of invective. Pale brows rising to his hairline, Nuada does a double take, mouth falling open. The only thing that looks vaguely like a weapon in the hall is my rather dilapidated umbrella. I should think lance trumps broken umbrella. Unexpectedly, he gives a small, formal bow, touching a hand to his chest.

"Forgive my rudeness," he declares, a quarter smile tugging his mouth. "I have been too long removed from polite company."

Flustered, I nod and hmph. He seems amused by a woman swearing. Again, the Prince has displayed how volatile he is. One moment he is drinking tea, the next flying into a temper, the moment after that, subdued by a woman raising her voice to him. Perhaps it was me appealing to the ancient laws of hospitality? Who knows. He looks at me, expression unreadable, tea mug in one hand, lance in the other. I see the centuries behind his eyes and I'm afraid it's simply time that is the cause. I'm afraid I'm too spiritually young for this, that I'll misjudge something and end up causing a catastrophe. I'm afraid of the quickening his presence causes in my blood, my womb, my soul. I'm worried that he'll see it and use it against me. I'm more worried he'll decide I am a hollow creature after all and take out my throat with his lance. I fear that he'll decide not to seal up the rip between worlds, if he is even aware it exists. Suddenly, the BPRD seem the least of the problems.

"I am lost," he says abruptly, the words bursting out of him. "A lost Prince, from a fallen kingdom."

He gestures, reaching for understanding that eludes him, regarding me with evident confusion. Setting down the cup, he moves toward me. Instinctively, I take a step back.

"Why are you helping me?" he muses, more to himself than me. "You know my name; your people know my history." He taps his temple, indicating the memories he stole from my head. "You were there when I tried to wake the Golden Army. I would have destroyed humanity had I succeeded. I am the monster your children should fear. You should fear me far more than you do, Aisling."

Fingers snaking around my upper arms with enough force to make me wince, he almost lifts me off my feet as he demands, "Why?"

Balanced on the balls of my feet, heart tripping, I reach out and place my right palm against his chest. I can feel the slow, steady pulse of his heart beneath the old cotton t-shirt. He looks down at my hand, like the contact shocks him, then back to my face.

"Because you're lost," I reply, relieved that my voice is steady. "Because what you've done is terrible, but what you can do now will go a long way to setting the balance right."

With that, I gently disengage his grip from my arms, thud down onto the third from bottom stair and pat the space next to me. As the Prince sits down, fluidly, expectantly, I take a deep breath and tell him about Nin Grey and the white owl.