Gisco’s words give me the chills. Come to think of it, it’s freezing up here. And the air is soupy thin. I feel dizzy, and I wrap my arms around my shivering body.

I flash back to Dargon in the volcanic cave, warning me that if I used Firestorm to save the oceans I wouldn’t be healing the future but rather destroying it. There would be a ripple effect, he claimed, that over the course of a thousand years might alter everything, including my ancestors. So was Dargon right? I ask Gisco. You can’t repair a problem by sending someone back in time to change the past? Did I muck up the whole future when I used Firestorm? Did I kill my own parents?

Calm down, Gisco urges. Dargon was wrong. He was playing on your unsophisticated understanding of time-space. We knew what we were doing. I can’t explain this to you, Jack. You don’t have the background to understand it. If you tried, it would just confuse and discombobulate you, to the point where you could no longer function.

I don’t have to do much functioning in this balloon, I point out. I’ll risk discombobulation. Fire away.

The dog still hesitates. The human mind is a frail thing. It can’t handle what it can’t wrap itself around.

I sense that Gisco truly believes this. Just try, I urge him. What happens when someone travels back through time and changes something?

The hesitating hound looks over at me, and takes pity. I’m a fool, Gisco mutters. But okay, I’ll try. You see, Jack, the best scientific minds of your era got this wrong. They wrestled with the same questions as you. Einstein battled with them, too. His Theory of Relativity first opened the door to the theoretical possibilities of time travel. And he didn’t like those possibilities one bit.

I think of Einstein—the wise old face with the playful, childlike eyes. That mental picture brings another image to mind—the old mummy’s face I saw in my strange dream on the dinghy, and more recently when he seemed to be flying through the storm clouds near us. I blink it away, and refocus on the Father of Relativity. I’ve read a lot about Einstein, I tell the dog. I know he thought the cosmos should be logical and beautiful.

Correct, Gisco agrees. And time travel is fraught with paradoxes. Einstein hated those. For example, there’s the Grandfather Paradox: If you travel back in time and kill your own grandfather before he meets your grandmother, then you would never have been born. But, at the same time, you were the one who killed him.

I try to digest this, and find myself holding tight to the side of the gondola. It’s a mess, I agree. Is there an answer?