Helium-filled balloons, tied to the gate, bobbled in the light breeze. As Strike walked down the steeply sloping front path to the door, the package Robin had wrapped under his arm, he told himself that it would soon be over.

‘Where’s Charlotte?’ demanded Lucy, short, blonde and round-faced, immediately upon opening the front door.

More big golden foil balloons, this time in the shape of the number seven, filled the hall behind her. Screams that might have denoted excitement or pain were issuing from some unseen region of the house, disturbing the suburban peace.

‘She had to go back to Ayr for the weekend,’ lied Strike.

‘Why?’ asked Lucy, standing back to let him in.

‘Another crisis with her sister. Where’s Jack?’

‘They’re all through here. Thank God it’s stopped raining, or we’d have had to have them in the house,’ said Lucy, leading him out into the back garden.

They found his three nephews tearing around the large back lawn with twenty assorted boys and girls in party clothes, who were shrieking their way through some game that involved running to various cricket stumps on which pictures of pieces of fruit had been taped. Parent helpers stood around in the weak sunlight, drinking wine out of plastic cups, while Lucy’s husband, Greg, manned an iPod standing in a dock on a trestle table. Lucy handed Strike a lager, then dashed away from him almost immediately, to pick up the youngest of her three sons, who had fallen hard and was bawling with gusto.

Strike had never wanted children; it was one of the things on which he and Charlotte had always agreed, and it had been one of the reasons other relationships over the years had foundered. Lucy deplored his attitude, and the reasons he gave for it; she was always miffed when he stated life aims that differed from hers, as though he were attacking her decisions and choices.

‘All right, there, Corm?’ said Greg, who had handed over the control of the music to another father. Strike’s brother-in-law was a quantity surveyor, who never seemed quite sure what tone to take with Strike, and usually settled for a combination of chippiness and aggression that Strike found irksome. ‘Where’s that gorgeous Charlotte? Not split up again, have you? Ha ha ha. I can’t keep track.’

One of the little girls had been pushed over: Greg hurried off to help one of the other mothers deal with more tears and grass stains. The game roared on in chaos. At last, a winner was declared; there were more tears from the runner-up, who had to be placated with a consolation prize from the black bin bag sitting beside the hydrangeas. A second round of the same game was then announced.

‘Hi there!’ said a middle-aged matron, sidling up to Strike. ‘You must be Lucy’s brother!’

‘Yeah,’ he said.