She had thought that the building looked like a birthday cake, but now she saw that it was more like a doughnut. She was in a ring of corridor, and through windows she could see that the heart of the ring was outdoors. She peered out. It was full of people, but they were clouded by a thin mist that seemed to cling to the place. She realized that she was looking at a glittering blue pool; the air was so cold that where it met the water, the water was shocked into swirls of vapour, creating the mist.

It was an outdoor pool, in December, in Budapest. Max shivered, and wished she had been given Rupert Nobes to follow. She was sure that he wasn’t doing anything this stupid.

But there was nothing for it: she changed into her costume, crammed her things into a locker, thought warm thoughts, and dashed through the freezing air to the waiting mist and icy blue.

To her surprise and delight, it was warm – gloriously warm – and full of unexpected bubbles. Every inch of her body sighed in relief. The pool wasn’t really a swimming pool: she could stand in it, and people were just lounging around enjoying the bubbles and chatting. It was more like one of those Roman baths she had studied at school. She cut through the water, trying to find Ester and Klaus in amongst the mist, pretending to be a submarine with just her eyes above the water.

She found Ester sitting by herself. She was squatting at one wall of the baths, eyes closed, a blissful smile smeared across her enormous jaw. Max knew how she felt. She turned a somersault through the bubbles, and they rippled and swirled around her, and she didn’t think her body had ever felt this light and content.

But where was Klaus?

A small tidal wave answered her, knocking her sideways midway through her second somersault, and sweeping two elderly ladies away to the far side of the baths. Klaus had arrived. He was wearing bright orange trunks and a blissful smile, and he splooshed joyfully in the water.

“Guten tag!” he cried.

But Ester was not on board with guten tag. For reasons that Max couldn’t comprehend, she was furious with Klaus. Her angry torrent of German scared off everyone that hadn’t been washed away by his tidal wave, leaving an empty semicircle of fury around the two of them. Ester was turning a reddish purple, and surrounded by the swirling mist, she looked terrifying.

Max bobbed at the edge of the semicircle, hidden by the mist. Why was Ester angry that Klaus was here? Did this hold any clues to who he really was?