He groaned inwardly. That was the end of Gillard’s plan to give Sam a pleasant surprise.

It was almost ten when he got home that evening. The report hadn’t been hard to write, but it lacked a conclusion, which made it feel unfinished and unsatisfactory. As Gillard reversed the car up the drive, he saw that Sam’s little black Renault was gone from its normal position in front of the garage, next to his RAV4. The usual lights in the house were on, in the hall and kitchen, plus one of the bedrooms upstairs. He let himself in and called her name. No reply. The burglar alarm had not been set. There was no note on the kitchen table, and no evidence of any meal except the unwashed breakfast plates.

Gillard checked his phone. He had sent Sam a text when he was almost finished with the report, to say when he would be home. That was just before nine, and there had been no reply from her, which was unusual. He rang her mobile, which was turned off. He left a message. This was all very strange. He went upstairs, and checked the lit bedroom. The bed was made, there was no evidence of a hurried change of clothing, which is what he would have expected if she had come in and then gone out again to see a friend.

A ragged edge of anxiety crowded his consciousness, but he refused to let it dominate. This was a problem of logic. Had Sam returned home at all? The kitchen and hall lights were on a timer, so would go on automatically at seven p.m. However the bedroom light was not, and he was pretty sure it would not have been left on when Sam left in the morning, because it would already have been light. That would tend to indicate she had come home. But why would she not leave a note or email or text him to let him know?

He checked the landline answer phone, which indicated no new messages, then logged on to the Internet upstairs in his office. He used Sam’s laptop and went straight to Facebook, which took him to her account. There was plenty of recent activity, particularly from Ellen, but no indication on direct messages of any hurriedly arranged girls’ night out. Sam’s parents lived in the Lake District, a major expedition, so she wouldn’t have gone to see them on a whim.

Baffled, and increasingly alarmed, the detective went back into the kitchen and looked around for evidence from first principles, as if it was somebody else’s home. Instantly he noticed the kitchen table was not quite in its normal position. Discoloured square marks on the linoleum, evidence of its usual alignment, were visible. One of the three chairs was not tucked under the usual edge of the pine table. He crouched down and peered under the table, and spotted something glinting in the shadows. An earring. A small dangly butterfly that he recognised as one of his wife’s favourites.