From the ground, where Sylvia and Agnes were watching, the sight of a hundred hot air balloons taking flight all at once was breathtaking. The air was crammed with colour and flame as red and yellow balloons jostled with pink and green ones for space. Some of the teams threw ribbons from their baskets as they flew over the watching crowds, making them cheer with delight.

From the viewpoint of two terrified cats, however, the sight was breathtaking in an altogether different way. Maximilian and Oscar watched in horror as the ground sank away far beneath them, the basket they clung to swaying alarmingly and every jolt threatening to throw them to certain death. The other balloons swung dangerously close to them, the baloonists calling out to one another, spurring each other to go faster and higher. Maximilian sank his claws still deeper into the wicker basket and squeezed his eyes tight shut.

“It’s a cat!” cried a voice from a basket nearby.

“No!” cried another. “Two cats!”

There were yet more shouts and Maximilian felt strong hands clasping him and his fur being disentangled from the sharp clutches of the wicker. Then he was being lifted gently into the air, a voice speaking calmly to him. He opened one eye and found himself face to face with a bearded man wearing a look of utter bemusement.

“A most handsome cat, but what on earth are you doing up here?”

“This one has been in the wars,” said his companion, who had rescued Oscar and was holding him up for inspection. “Look at that eye. I bet he lost it duelling for a young lady cat’s honour.”

“Indeed I did,” Oscar miaowed. Maximilian smiled wryly. Oscar had at least a dozen stories for how he had lost his eye, but this was his favourite.

“Well, cats, whoever you belong to, you will have to wait till the end of the race to return home. We must make up for lost time if we are to have a chance of winning,” said a third man, who was working away at a series of pulleys underneath the balloon canopy. “And speaking of that…” He pulled on one rope and with a roar of flame the basket rose higher and shot forwards, past a basket full of women blowing kisses to the crowds below.

Maximilian miaowed his “but we were on the trail of a suspect and must get back to the ground at once” miaow, but the man holding him just laughed and lowered him on to a ledge that ran around the inside of the basket and served as a bench for its passengers to sit on.

Oscar leapt to join him, peered over the side and looked down. “No chance of getting out now, I’m afraid, my friend,” he said. “We may as well just enjoy the view.”

Maximilian had no intention of looking over the side of the basket. Much as he now loved his rooftop walks with Oscar, he was still not keen on heights that swung so alarmingly. He preferred the safety of a solid window sill or chimney pot. He remembered how he had laughed at Peppi for his nerves that first night they had taken him across the heights of Paris and felt thoroughly ashamed of himself. He was just as nervous now as Peppi had been then.

“Take a look down,” Oscar said. “It really is the most incredible sight.”

Maximilian opened one eye and gasped. From high up in the balloon, Paris spread like a glorious map beneath them. In the park below, laid out in its neat squares and curved fountain walks, the people looked like small dolls. In a few minutes they had left the park and were soaring over the city, a carpet of cream stone and greenery. The balloon carried them over packed streets where shoppers jostled for fresh cheeses and meats, and above the curves of the beautiful Seine river, glittering in the spring sunshine.

As they were nearing the wonderful Eiffel Tower, whose top platform was crammed with tourists waving flags in a myriad of colours, eager to catch sight of the balloon race, Maximilian spotted a familiar figure far below, weaving nimbly through the crowds: a woman dressed in black with a yellow handbag. He was sure it was Zelie. She paused at the door of a house and, as she looked up to the balloons, the sun glinted off the monocle over her left eye.

“Oscar, quick!” Maximilian hissed. “That’s Zelie. We must remember how to get back here.”

Oscar nodded and together they scanned the streets below. Oscar murmured to himself, “Two streets to the left of the river”, while Maximilian memorised the sight of the stationer on the corner of the road and the wide, sweeping avenue that led down to a children’s playground. He squeezed his eyes shut and found he could see a perfect picture of the streets below in his mind. He squeezed again, as if setting off a camera shutter, and then opened his eyes and looked at Oscar. They made a brilliant team. Zelie would be no match for them.

It was a few minutes later that the balloons finally began to descend towards an open piece of parkland in the west of the city. The sun was still high in the sky, and the white stone of the buildings surrounding the park glowed like jewels in the golden light. The balloons floated down in clusters, the cries of delight from the crowd and the race teams mixing with the sound of baskets bumping along the ground. The grass rose to meet them and as they thudded down three men rushed to steady the basket, slapping the team on the back and greeting them excitedly.

Maximilian grinned at Oscar and the two of them leapt from the basket, miaowing their thanks to the men who had rescued them. Then, being very careful to avoid being caught up in the ropes and baskets and canvases of balloons that were being deflated and falling with deep sighs to the ground, the two cats set off to find Zelie.