“We are going to see colossal environmental changes as time goes on,” Khan continued. “Invasive species from other timelines will be turning up all over the world. And we won’t be able to eliminate these new arrivals or prevent them from coming. We’ll have to work with what we’ve got.

“And there will be some intrusions that will require the action of diplomats, not conservationists. There will be intelligent entities who stray into our world by accident, and those who come here because they are fleeing privation or persecution. There will be people from our world who fall through the gaps to elsewhere, and those who choose to leave. There are worlds out there that will need protecting from us, and worlds we will need protection from. We are entering a new age of our planet’s history. And while we have staved off Armageddon—for now—that doesn’t rule out this being an extinction-level event for humanity.

“If the governments of Earth, our Earth, can get their act together and put away their rivalries, we can rise to face these challenges together. And the time to start working on these future problems is today. I can’t stress this strongly enough. Speaking as an academic, a scientist, I have no power to force such cooperation or such foresight. I can only state my case as forcefully as possible and hope that sane minds prevail. But that’s on you, all of you.”

She took a deep breath and leant back in her chair. She was drumming the fingers of one hand on the desk, which Julian knew meant she was desperate for a smoke. The recording had taken nineteen attempts, after all. Everyone involved had been getting short with one another.

Ertil tapped politely at Kay’s elbow. “This is Ertil,” she explained. “His people live next door to our world, or just about. Some of his people are already in our world, and there will be more. They’re also ahead of us, technology-wise. They’ve cured cancer! How about that? They could potentially do a load of good for everyone.” She glanced to her other side, and Murther shuffled into view.