way.’
‘There’s no sign of him.’
‘He must have left some kind of trail. Keep looking around.’
‘Bimsley, how long since it stopped raining?’
‘Twelve minutes, sir.’
‘The levels will be falling. We should try to find an exit. Call Longbright and find out where the nearest drain shaft is, would you?’
Bimsley tried his phone, but failed to locate a signal. ‘No response. We’re in pretty deep ground.’
‘So we’re on our own. I wouldn’t fancy our chances of climbing those slopes back up. We’ll have to go on,’ said May.
‘Very interesting,’ said Bryant approvingly. ‘The Fleet was choked off by the expanding metropolis, but its waters still ran, albeit at a fraction of their former power. And at the highest flood levels, the water would fight to find a way around the obstacles. The system is beautifully simple when you think about it. The engineers knew the floods were cyclical over decades, so they allowed for the Fleet to return by a series of self-controlled gates that can only be opened by a specific volume of water. Under such conditions, the river cuts a path all the way through the local district conduits to form a single united flow heading to Camden Town and Clerkenwell, following the old route just as it used to, before emptying out into the Thames.’
‘Yes, Arthur, and as soon as the level drops and the weight recedes it will switch back, leaving us, all too literally, I fear, dans la merde. So can we push on?’
‘Let me see the map again.’ Bryant held it beneath his torch.
‘I can hear something,’ warned Bimsley, putting his ear as close as he dared to the wall. ‘It doesn’t sound good.’
They shone their torches back to see the first of the great steel plates grinding across on its arc as the Fleet redirected itself back to local channels. The group pushed on and down as the water started to deepen. ‘It’s probably refilling from the highest gate first,’ warned May. ‘I doubt any one gate could handle the full amount of water, so the switch-back will be staggered with locks, but the effect will still be like flushing a cistern. The water has to maintain a momentum in order to reach the river. We really have to find a way out of here.’
‘You can hear it coming,’ called Bimsley, an air of panic creeping into his voice.
‘The sound is probably magnified,’ said Bryant cheerfully. ‘It’s echoing down the entire length of the shaft. According to the map there’s a drainage shaft down here on the left.’
They found themselves in another dead end filled with the detritus of the past thirty years. As they pushed through the rubbish, the bloated corpse of a cat swirled by.
‘Sorry,’ Bryant apologized, squinting at the plan. ‘Now a right turn—it’s hard to read the scale of this thing. It should be right here in front of us.’
‘There’s your shaft,’ said May, reaching a halt. ‘Somehow I don’t think we’re going to make it out of here.’
‘Why do you say that?’ asked Bryant.
May shone his torch up to the roof, illuminating the chimney to the surface, more than thirty feet above their heads. ‘The ladder is missing. There’s no way of reaching the drain without it. And we can’t go back.’
Bimsley pinched his frozen nose and tried to think. ‘There were three corridors at the last junction. We know that two are dead ends, so let’s go back to the first one.’
‘Admirable idea, Bimsley.’ Bryant struck out through knee-deep scum. ‘The water’s much warmer than I thought it would be. I think it’s coming from a heated source—dishwashers and washing machines, perhaps. There’s a distinctly soapy smell now.’
‘Arthur, I think we should concentrate on the problem at hand.’ May towed his partner back until they reached the junction. They turned into the only remaining tunnel as the rumble of water rose to a roar behind them. They had gone less than a hundred yards when the corridor narrowed sharply and twisted off.
‘Fingers crossed,’ called May, wading ahead. ‘If this doesn’t lead out, we won’t be going home tonight.’
He was almost frightened to raise the torch.
‘Well?’ called Bryant.
Bimsley followed the beam across the now thigh-deep water. The tunnel appeared to open out to a much larger space beyond, but there was no way of reaching it: a matrix of scabbed iron bars blocked the way ahead. May slammed his fist against the metal as he realized the impossibility of moving it.
‘There’s a grille across the outlet,’ he called back.
‘Can you open