They followed the old woman along the beach to a point where a broad black rock emerged from the sand, the visible part of some greater mass below. It was like a great stone doormat marking the entrance to the causeway. The old woman stepped onto its worn surface and went straight out into the wash of the sea. Clariel and Bel followed, both letting out a slight gasp as the cool water splashed around their legs, the wavelets coming around the Islet sometimes washing up as high as their thighs.

Looking down through the swirling water Clariel saw that they were standing on a kind of bridge of stone that was at least a foot higher than the surrounding sand. At the lowest tide, it would be completely dry, but judging from the tidemarks on the beach and the green stain on the city wall some hundred paces away, at the flood the Islet would be cut off by deep water. It would certainly be well over Clariel’s head, and the tidewash would be powerful.

As both Kargrin and the old woman had said, there were stones marking the sides of the causeway, which was about twenty paces wide. Roughly pyramidal, the markers were obviously man-made, but had been worn long in the sea. They were covered in green weed and the purple-grey shells of lippets, shellfish that could be eaten or used as bait for fish, though neither humans nor fish were particularly fond of the strong-tasting bivalve.

‘Good defence against the Dead,’ said Bel quietly to Clariel when they were about halfway across. A bigger wavelet had just swept past them, drenching them up to their waists. ‘Sea currents and waves are as effective as a strong river flow.’

‘But the sea doesn’t stop whatever this Free Magic thing is,’ said Clariel, keeping her voice low, so the old woman ahead couldn’t hear them.

Bel shrugged. ‘Maybe it crosses when the causeway is dry.’

‘The aqueducts don’t dry up,’ said Clariel. ‘And apparently it passes under them as well.’

‘Yes, there is that,’ replied Bel. ‘Look, I’m not going to run if we do find this creature. No matter what.’

‘Then you’re an idiot,’ said Clariel.

‘You don’t understand,’ said Bel. ‘I’m an Abhorsen, this is what we do –’

Clariel stopped, and turned to face the young man, both of them briefly rising up on tiptoe as another wavelet washed past them.

‘I don’t care if you get yourself killed. But don’t mess things up. My parents keep going on about opportunities for me in Belisaere. This represents an opportunity for me to get out of Belisaere and it might be my only one, so don’t spoil it!’