They suspect the blue light is connected. The light comes on before K and M come out. If only K comes out the light may go off, but then it comes back on. The five have worked out the light operator doesn’t know when K is coming back as sometimes K waits for a few minutes and sometimes the light comes on just before he gets back. That means there is no communication between K and the light operator. The five also surmise that M operates the light because when both K and M go out the light stays on until they go back.

‘He must be mad,’ Malcolm says to Konrad, shaking his head, oblivious to the surveillance. ‘He only woke up two days ago . . .’

Ben must be awake. Harry hurt Ben. Ben was unconscious.

‘Training hard though, so he’s determined,’ Konrad says.

Ben is training for something.

‘When’s the swimming tank getting here?’ Malcolm asks as they walk down the street.

Alpha nods to Charlie and Bravo, who move off towards the back door to thread down through the maze of alleys to the main road to begin the foot follow.

‘In an hour,’ Konrad says.

Alpha listens through the headphones. Swimming tank. They said swimming tank, not swimming pool. A swimming tank is a single-person training device equipped with a current generator to allow a person to remain static and swim against a flow of water pushed from a machine. Ben is training. They are waiting for a swimming tank. Ben is training to swim for something.

‘He’s a different man,’ Malcolm says, the voice now fading as they walk down the road. ‘Like when he first got here . . .’

Konrad replies but the words are lost to a static hiss.

The intelligence picture grows. Pieces of a puzzle that are fed into the system and put together by experts under the ever-watchful eye of Mother. Harry and Safa went into a water environment using the RIB. They did not survive, but straight after that is when Doctor Watson was first mentioned. It is suspected Harry and Safa rescued the doctor but died in the process.

Alpha, Delta and Echo wait. Bravo and Charlie foot follow. Malcolm and Konrad go to the café. They drink coffee. They come out and walk further into the city to a specialist diving store. They purchase small tanks of compressed air. Three of them. They purchase flotation devices, wetsuits, diving knives, rope, flippers, diving masks and all manner of equipment associated with scuba diving.

‘M and K back,’ Echo says, watching the end of the road.

‘. . . but it feels horrible without them,’ Malcolm says, grimacing at the weight of the bag on his shoulder. ‘Like empty . . . six months they were there . . . six months . . .’