There, leading into the shallows, in the mud that had been exposed by the lowered water level, were the imprints from three wheels—two large ones with a smaller one in the middle. Three tyres, possibly a three-wheeled stroller, exactly like the one they were searching for. There was a scrap of dirty black fabric caught in one of the tyre tracks. She took out her phone and snapped several pictures of its position, then bent towards it, poked the scrap out with a pen and bagged it. Then, she searched the surrounding area for matching tracks. There were none. The stroller had gone into the water. But Harper couldn’t see any immediate evidence of where, or if, it had come out again.

“Constable, we need to search the river. I mean, in it, not just the path.”

“But boss, it’s so shallow, we’d have seen it.”

“Just get a diver down here, now. It’s not all shallow. Look.”

He followed her gaze up the river, to where a bend formed a dark pool under the trees. In that small section, you couldn’t see the bottom. The water could have been two metres deep. It could have hidden a stroller, easily. There would be pools like this all the way up and down the twisting Bishop. And of course, the river joined the deep and murky millpond further down, where whole cars had sunk without trace. Harper banished a vision of the sinking stroller, the helpless babies strapped in, sucking water into their little lungs. It hadn’t happened, it couldn’t have. Somewhere in her mind she just knew that it hadn’t, but she couldn’t trust it. The knowledge was mixed with both hope and uncertainty.

“You go and look at the millpond, see if there’s anything to be found there, tracks or footprints,” said Harper. “I’ll go that way.”

The constable set off immediately in the downstream direction, while Harper went the other way, intending to note where the deeper parts of the river were, all the possible places where a person might submerge a baby’s pushchair. She wanted some useful information to direct the divers when they arrived to start searching in the water. Trying to remain detached, she pushed away the queasy feeling that came in waves when she thought of the babies under the water, or the fact that she might be too late to save them.