‘I give you a riddle,’ Olsen said suddenly. ‘It is black. It has eight wheels. But it is no vehicle. What is it?’

His penetrating, slightly protuberant eyes surveyed them as they shook their heads.

‘What is it?’ he repeated.

‘We shall not find that,’ Josef said.

Olsen gave a short laugh. ‘A priest, on roller skates. I give you another riddle. It is greater than the universe. It is less than a grain of sand. The dead eat it. If we eat it, we too shall be dead. What is it?’

‘We shall not guess that, either,’ Josef said.

‘We give up,’ Sheila said.

‘Greater than the universe,’ Olsen said. ‘Smaller than a grain of sand. The dead eat it. If we eat it, we die also. What is it?’

‘You will have to tell us again, I’m afraid,’ Jones said.

‘No. Think of it. If you cannot guess I will tell you another night. But now you can think.’