Mark's room

We retreated to the safety of Mark's room, where I sat on the unmade bed while he paced for long tense minutes before finally breaking the silence.

"So," we both say almost in unison, "we should talk."

I couldn't help giggling at the coincidence and Mark responds with a warm chuckle

"Ha ha," we both said, "but seriously I've got something to tell you and I need you to listen..."

The second time, the weird synchronisation was less amusing. Mark's dark eyes flashed with annoyance, even though he was obviously the one copying me.

"Come on, stop that," we grumbled, "I mean it. Stop that young man."

At last, a difference. As I said young man, he called me a young lady. Which didn't improve my mood much, but did at least show there were limits to his ability to copy me

We glared at each other, although why he was annoyed with me, I couldn’t imagine.

"Fine," we both snapped in the end, "ladies first I guess..."

"Okay," I managed at last without an echo this time, "this is probably going to sound crazy, but I'm not actually your sister. I'm in her body, but I'm really your father."

"No way!" He looked as shocked as I'd have expected, but what he said next caught me completely off guard, "I thought you might be but still it's still hard to believe."

"I assure you I'm telling you the truth," I insisted, trying to put as much patriarchal authority into Kelly's voice as I could manage, "I can prove it..."

"No, no," Mark interrupted me, "you don't understand, believe you, but the thing is I'm not me, uh, I'm not Mark, I'm David too."

We stared at each other in mutual confusion. He had to be lying for some reason, I was sure of it. And yet...

He certainly wasn't acting like the son I knew. The way he held himself, the way he spoke. He'd called me princess, my pet name for Kelly. He'd known exactly what I was going to say as I said it...

"Okay," I said after he'd explained his theory that the strange app had somehow duplicated my, or should that be our, consciousness, "let's say you really are me, what the hell do we do now?"