“What about the boy they arrested?”

“Nick Mardle. He seems lonely, a bit disturbed. Perhaps a little immature. I don’t think he has many friends, except Mark, who was there too. Mark Taylor. He seems quite harmless. You’d like him. He’s a student. He had a crush on Elizabeth, but I think her pregnancy brought him to his senses … I don’t know how to describe Jerry Packham. I always liked him, but now I think perhaps I didn’t know him very well. He was having an affair with Pamela Marshall.”

“Charlie Todd’s niece?”

“Yes. And that has confused the case. Because they were both members of the same family, Savage has the theory that it was some sort of psychopathic revenge killing. I’ll tell you why I don’t believe that, later.”

“All right,” she said. “ Who else is there?”

“Jasmine Carson. A retired schoolmistress. So much the stereotyped schoolmistress that I wonder sometimes if she has anything to hide. She’s efficient. She’s the one who really runs the observatory. Doctor Derbyshire thinks that he does, but he’s a ditherer. He’s good with figures, with abstracts, but he isn’t any good at taking decisions. I can’t quite work out why he still comes to the observatory. He hardly does any ringing now, and doesn’t even go out on to the island much. I think, when he was younger, he was quite a keen ringer. I’ve seen very sound papers by him in some of the more academic natural history journals. He was always specially interested in seabirds. He used to go ringing on sea cliffs in Scotland and the Hebrides, but you can’t imagine him dangling at the end of a rope now. And today I’ve learned that he has other, rather more sinister, interests.”

He described his meeting with Jasmine Carson, the contents of the letter she had found in the doctor’s room.

Molly stopped. George had set a brisk pace and she was hot. She felt very exposed. They were alone. The sand and the mud stretched for miles, and no one else was on the shore. The sun was very low and reflected in the water all around them. Only the island broke the line of the horizon. They were close enough to see the detail of it, the white wall around the observatory, the fissures in the low, crum bling cliffs, the sycamores around the wooden frame of the Wendy House. She took off her rucksack and did not object when George picked it up. Then she took off her mackintosh, rolled it roughly into a sausage and tied it around her waist. She turned her face to the breeze. She was recovering her breath.

“What’s worrying you?” she said. “ Why don’t you think that it was the boy?”

He walked on more slowly, and she followed him.

“Partly it’s the boy,” he said. “He’s mixed up, but he’s not a psychopath. I believe him.”

“Would they let me see him?” she asked. She was remembering other lonely, mixed-up young people. They had been her livelihood. When she had worked as a social worker she had befriended, been hurt by so many.