“Are you sure you’ll be ok, Annie?” fussed my Mum, as my Dad picked up her suitcase to take it to the car.

“And I hope you haven’t advertised your party on Facebook,” said my Dad with a smile. “I don’t want to switch on the TV in Devon and see our house going up in flames, with hundreds of drunken youths on the rampage in the street.”

“Oh Dad, it’s only my best friends, honest,” I said. “And no boys at all, I promise.”

“Take no notice, dear,” said my Mum as she kissed me goodbye. “You know he’s just winding you up.”

I was looking forward to having my friends over while my parents were away for the weekend. My brother was off camping with his school, so he’d be out of the way, meaning we wouldn’t have to worry about him mooning about and ogling my friends. Even so, it was good of my parents to let me have them over; I was quite pleased that they seemed to trust me now that I was in the sixth form at school.

The first to arrive was my best friend, Penny. I gave her a hug, and took her upstairs into my bedroom to change into her night things. I watched while she pulled her t-shirt over her head. She was wearing a pretty, lacy black bra that pushed up her large tits, forming an attractive cleavage. She unbuttoned her shorts and slid them down her long legs, revealing a pair of lacy panties that matched her bra.

“Nice one,” I said, laughing. “You’re actually matching today.”

Penny stuck her tongue out. It was a running joke in our group that she never managed to match her bra and panties.

“And now I’m not even going to keep them on,” she said, as she slipped the straps of her bra down and unclipped it. She bent over and rooted about in her bag for her nightwear, her bare tits swinging and her bum in the air.

She took out another t-shirt and slipped it on. Then she looked at me.

“Is it a knickers-on or knickers-off party?” she asked with a smile.

I didn’t say a word, but pulled up my little nightie to show that the dress code was definitely knickers-off. “Right-oh.” she said, and pulled hers off as well. Her t-shirt wasn’t all that long, and when she raised her arms her bare pussy was only just covered. Mind you, my nightie was quite low-cut and loose, and kept slipping down, letting my nipples peep out over the top. We looked like a right pair of dirty girls.

During the next half an hour or so the other girls arrived and changed into their night gear. There were a few not-too-serious protests when the “knickers-off” rule was announced, but everyone complied in the end. Honestly, it looked like the set for a cheap “teenie” porn movie, with all the barely-covered tits, bums and pussies jiggling about. There was much excitement when one of us, an apparently demure girl called Alison, took off her bra and revealed that she had a nipple piercing. She was quite happy for us all to have a good look, and I couldn’t help feeling slightly jealous at all the attention she was getting, with everyone wanting to touch and play with it.

When I’d sent out the invitations to all my besties, I’d told them that this was going to be a sleepover party just like we’d had as little kids, with party games, cheesy music, and jelly and ice-cream to eat, but without the parents to tell us to shut up and go to sleep. I’d dug out some girly DVDs for later, but I decided that we were going to start off with a game of hide-and-seek. We’ve got a pretty big house, on three floors with an attic, so it’s great for this sort of game.

We drew lots to see who would be the “seeker,” and Penny lost. She went into the kitchen and started to count to 100, while the rest of us scattered up the stairs, giggling and pushing.

Obviously, as it was my house, I had an advantage. I knew that my parents’ bedroom had a large fitted wardrobe all along one wall where I could squeeze in nicely, and that was where I headed. Carefully, I opened the door, slipped inside, and tip-toed across the carpet to where the wardrobe loomed out of the dark. Opening the right-hand door, I pushed in among a selection of my mum’s dresses, and carefully pulled the door shut behind me. I hoped that if I pushed myself far enough back, Penny might not see me even if she opened the door.

I’d only just pulled the wardrobe door shut when I heard the bedroom door open. I assumed that it couldn’t be Penny yet, since she would still be counting, so it had to be one of the other girls. I kept quiet and listened to her moving quickly around in the room, looking for somewhere to hide. Then to my annoyance I heard her outside my hiding place, and the door of the wardrobe began to open.

“Go away,” I hissed, “This is my place,” and the door closed again. Then I heard the door to the adjacent part of the wardrobe open, and whoever it was squeezed in. They must have had to crouch right down, because there was a shelf at about waist height, although the lower part of the wardrobe was open all along the bottom. I heard the door pull shut, and there was silence, apart from a few rustles as my fellow hider tried to get comfortable.

Soon all I could hear was my own breathing, and that of my invisible companion to my left. With the lights out in the room, the curtains drawn and the doors to both the bedroom and the wardrobe fully closed, it was pitch black, and I couldn’t see a thing. Hemmed in as I was by coats and dresses hanging around me, I couldn’t move much either, and was starting to feel quite warm. From my left and below, I heard the sound of a body shifting slightly. Then I almost cried out as I felt something warm flicker across my foot. For a moment I thought it was a mouse and nearly burst out of the wardrobe with a shriek, but then it came back more slowly, and I realised it was someone’s fingers: my invisible companion!

I soon guessed what she was up to; she was trying to make me giggle and give myself away. I am awfully ticklish, and I tried at first to pull my foot away and stand on one leg, but the fingers just found my other foot instead, so I nearly fell over.

Then I felt the fingers move up my bare leg, around and over my calf, tickling the soft area at the back of my knee. I leaned against the back of the wardrobe, biting my lip to stop myself giggling.

Then my heart gave a little lurch as the fingers moved a bit higher, and suddenly they weren’t tickling as much as stroking, kneading the firm pliant flesh around the back of my thighs. That felt really nice; too nice. The whole hand began to rub against my warm flesh, delicately and tenderly. Almost imperceptibly, I could sense it moving further up my thigh under my nightie. This wasn’t tickling any more, this was definitely caressing. Oh god.

The invisible fingers seemed to hesitate; either because they couldn’t reach any higher, or because their owner wasn’t sure whether she dared go any further. “Oh God, don’t stop now,” I thought. Quickly, before the hand disappeared, I grasped my nightie with one hand and pulled it right up above my waist, while simultaneously bending my knees slightly to allow the hand to climb higher.

To my delight, it did, moving up over the really sensitive flesh at the top of my inner thighs. The anticipation was almost unbearable. Then at last I felt the fingers reach their goal, the spot where my bare thighs met; where the opening of my wet slit lay between the folds of my labia.

Gently the fingers rubbed at the entrance to my slit, sliding up and down it. I felt myself starting to tremble even more, wanting the fingers to go further, but sensing that I shouldn’t speak or try to guide them. That wasn’t part of the game. But I gently slid one foot sideways across the floor of the wardrobe to spread my legs slightly, making access easier.

I couldn’t help thinking that at any moment the seeker might come into the room, open the wardrobe, and spoil everything. I so didn’t want that to happen.

Then, at last, I felt a finger probe further between the folds of my labia and (ah yes) slip up inside me. I gasped as I felt it moving gently, pressing against the soft spongy moist walls of my tight vaginal passage. Then a second finger joined it, and I could tell they were scissoring inside me, wiggling left and right, then up and down. I felt a trickle of juice running down my inner thigh.

Whoever it was seemed to know instinctively how to vary their movements to best effect. The fingers gave a few deep thrusts up into the depths of my tight wet passage, then curled up against my soft g-spot. I couldn’t help letting out a little gasp.

I really was tingling all over by this time. I slipped one hand inside the top of my nightie and found a warm firm breast, kneading it gently and feeling the nipple rising up hard and aroused. I pressed my other hand against my plump mound and could feel the fingers moving inside me as I began to rub at my clitoris.

I could hear the squish, squish, squish as the fingers thrust deeper up into me. I felt sure there must be three of them now, going as deep as they could. Reaching down to find some lubricating juices for my clit, I just touched them briefly. My own fingers were skidding over my clit now, and I knew my orgasm was near. From the rapid sound of my breathing, my companion must have guessed as much, because the fingers curled up and pressed against my g-spot. With a shudder, I came, almost losing my balance, but just managing to stay upright as my legs shook and the electric shock of my orgasm travelled to every extremity of my body.

As I struggled to control my breathing, I felt the fingers slip out of me. I let my nightie drop back down and just stood there in the pitch black, glowing all over. I was quite glad no-one could see me, as I must have been very pink in the face. My own fingers were slightly sticky, and I wiped then on one of my Mum’s dresses, hoping it would dry cleanly.

While I was doing this, I heard the wardrobe door click, followed seconds later by the bedroom door opening and closing again. Fuck-a-duck! My companion had gone, obviously not wanting to give away her identity when the seeker eventually found her way into the bedroom. I wavered indecisively, wondering if I should go after her, but of course by then it was too late.

It seemed like hours, but it must have been only a few minutes later when I heard the bedroom door open again, and footsteps padding quietly over the carpet. They stopped, and I guessed that their owner was looking under the bed. Then the feet came closer. I held my breath, pushing myself further back among the contents of the wardrobe, but the door opened and the seeker, Penny, let out a cry of delight.

“Gotcha at last, Annie,” she giggled. “You’re the last. I didn’t think you’d be in here, but then in the end I’d searched everywhere else. I should have checked here first.”

We went downstairs, Penny triumphantly and me hoping my recently-aroused state wouldn’t be obvious to everyone. Although there was much giggling and congratulations when we turned up, my friends decided that I’d had an unfair advantage as it was my house, and tickled me until I agreed that I’d cheated and someone else had won.

But one mystery remained. Who had been my invisible companion? I looked at each of them, hoping to catch either an embarrassed blush or a conspiratorial wink, but no, there was nothing. Whoever it was, they were doing a very good job of acting innocent. It was all very frustrating. I did wonder for a while if they’d even known it was me, although I guessed they must have recognised my voice when I told them to get lost.

All through the rest of the evening, I kept wondering whose probing fingers had been up inside me. I didn’t know if any of my friends were lesbians or bisexual, but I couldn’t help wondering if it has been Alison. She had seemed to get a lot of pleasure out of having her pierced nipple played with.

I wondered if I should confide in Penny, but wasn’t sure I could trust her to keep her mouth shut. Did I want everyone to know that I’d stood still and let someone invisible masturbate me like that? Not likely. I even thought about grilling her about where and when she’d found people, in case that gave me some sort of clue, but decided that would just look a bit too weird.

So in the end, I decided I’d just have to keep wondering, and hope that maybe my agile-fingered friend would decide to reveal herself at some point in the future. I made lots of innocent comments about how much I’d enjoyed the hide-and-seek, and hoped that might do the trick. After all, I felt that I’d rather like to return the favour at some point.