At 02:14 on a wet Tuesday the Irish Sea was behaving itself, which was exactly what bothered Priya Nair. She had worked the Cable Desk for eleven years, long enough to know that a quiet sea was not an empty one. On the wall in front of her the traffic lanes glowed in tidy amber: ferries to Dublin, a tanker waiting for the tide, a dozen fishing boats drifting like dropped salt. Everything moved the way it was supposed to. Nothing, apart from one small blue triangle off Anglesey, was moving at all.
The triangle was called MV Halcyon Survey. Its broadcast said marine research, crew of nineteen, destination Milford Haven, and for six hours it had held position over a pair of fibre-optic cables that carried a startling share of the country's data. Research vessels do that. They park, they sample, they leave. Priya had approved a hundred like it. She made herself a tea and watched anyway.
At 02:40 she saw it. Every forty minutes, almost to the second, the Halcyon moved in a small neat circle, perhaps two hundred metres across, then settled back over the cable. Nobody surveys the seabed that way. Surveyors work in lines. Circles are what you do when you want to be seen from above, or when someone wants you to think you are being seen.
She rang Dev Okafor at the coastguard liaison office, who answered on the sixth ring with the voice of a man who had been asleep standing up. “Weather hold,” he said, when she explained. “They're waiting out the swell.” “There is no swell.” A pause, the creak of a chair. “Then they're waiting for something else,” said Dev.