She’d turned, instead, to his men. “Gentlemen, let me reassure you!” She spoke earnestly. “We think of dowsing as a force for good. Life-enhancing … like bell-ringing or flower-arranging …” Her spine, already straight from three decades of corset-wearing, straightened even further, and she looked them directly in the eye. “In this Society, we stand in the Light. The occult is not even acknowledged by us. Will you accept that we put out no welcome mat for the Devil? That no supernatural presence crosses our threshold?”

“Not unless’n Old Nick were to get your signed permission first, miss, I reckon,” Sam drawled.

“An’ always supposin’ ’e remembered to wipe ’is boots, miss,” Joel added, straight-faced. “Good enough, Sam?”

“Good enough. ’Ave a go, shall we?”

They spat on their hands and held out rough palms for the hazel twigs.

In spite of their compliance, Hermione wasn’t quite sure they’d understood the finer points of the science of dowsing when she’d tried to explain. Indeed, when she’d attempted a demonstration of that pivotal stage—the rising of the rod—they’d gone into helpless convulsions with much flapping of red-spotted handkerchiefs, wiping of eyes and shaking of shoulders. Strong shoulders though.

And warm hearts, Hermione guessed. At any rate, their scepticism had an edge of amused indulgence. And it was silent, unlike the all-too audible sniping of the professor.

“All present and correct, Hermione, my dear,” announced the colonel. “Dawn coming up like thunder behind Tower Bridge downstream. Time to make a start? Yes?”

Hermione silenced him by extending a finger dramatically toward the river. “A minute or two spent in reconnaissance is never wasted, Charles,” she said, reining him in sweetly. “As you well know! You can give us all a lesson in preparedness.”

The peremptory finger redirected itself to the map she held in her other hand. She peered at it and raised her prow of a nose to align with the silhouette of Battersea Power Station just emerging from the mist on the southerly bank opposite. “Yes, the tide’s out and we have the right place. Last reminder, folks—we have one hour and forty minutes of low tide. I’m going to ask the colonel to plant this red flag at the edge of the foreshore.” She held up a triangular piece of red cotton attached to a pea-stick. “Keep an eye out at all times. When the water reaches this flag, abandon whatever you’re doing and move back to the embankment fast. Spring tides have swept many an inattentive mudlark away! I suggest we confine our search to the fifty-yard stretch from that upturned old boat on the right and the breakwater to the left. We’ll put Doris in from this side and Jack in from the other.” She smiled encouragement. “With our two best bloodhounds straining at the leash, what’s the betting that we shall soon be shining our torches onto … Roman denarii, evidence of Caesar’s lost river crossing …?”

“A piece of statuary wouldn’t be bad, would it?” The professor deigned to make a contribution. “They found the severed marble head of the Emperor Claudius in the river—perhaps with your additional supernatural skills, Miss Herbert, you can supply the British Museum with the imperial torso to go with it!”

“Or—better still!—a Celtic warrior’s shield.” Hermione reclaimed the spotlight. “It was a few yards from this place”—she turned to direct her remarks helpfully towards Sam and Joel—“that the most lovely, bejewelled bronze shield was dug from the mud. Why here? Did it indicate the site of some ancient battle? Or a devotional spot where precious objects were broken up and thrown into the water as a gift to the River God? To Father or Mother Tamesis? If you want to know more, you may ask the professor.” She turned a beaming smile on him.

“Now—how may we best deploy you, Reginald? Why don’t you sit yourself down on that boat? Check it for rats and rough sleepers first. From there you can watch our antics with your usual jaundiced eye and stand by to be consulted. Perhaps before we hear the chimes of Chelsea Old Church behind us calling us to coffee, you will be planning a new chapter in the history of Londinium?”

All were now primed and ready and at the right pitch of eagerness to start. “Did you all bring a flask? Excellent! Well, let’s get at it, then. You know what to do.”

RED FLAG IN hand, Colonel Swinton turned to the river to conceal his smile. In Hermione Herbert, the British Army had missed out on an effective field marshal. But she hadn’t been lost to them entirely. As a casualty of Cambrai, Swinton had, himself, encountered the full force of Miss—or, as she was then, Matron—Herbert’s efficiency. He’d noted her leadership qualities from his hospital bed and had always reckoned it was the ministrations of this angular, grey-eyed angel that had saved his life.

He’d watched her skilful disposition and motivation of her troops; he’d admired the cheerful way she’d snipped out the professor’s sting, rendering him not only harmless but even an asset. All was going according to plan though he would not relax his vigilance. The colonel was accustomed to taking responsibility for events and people, for quietly managing outcomes. So far, so good. No need at all for crossing fingers.

DORIS DA SILVA wasn’t experiencing the colonel’s sunny confidence. She sidled timidly to Hermione’s side and began to whisper. “Excuse me, Miss Herbert, but I really don’t like this place. It’s creepy!” She looked over her shoulder with what Hermione considered an irritatingly girlish show of fright. “There’s someone watching us. I’m not at all certain I can bear to work here.” She took a scented lace handkerchief from her pocket and put it under her nose. “And what’s that dreadful stench?”

“Just normal river smells, Doris. Oil mostly. With a dash of Lots Road power station effluent thrown in. Possibly a dead dog or two. Detritus of one sort or another. Brace up! You won’t notice it after five minutes,” she lied cheerily. Four years of military hospitals, blood, gangrenous flesh and mud had never accustomed her to the smell of decay. She woke on some nights with her nostrils still full of the ghastly cocktail that no dash of eau de cologne seemed able to dispel.

“Now come along, Doris—you’re trembling so much I’m not certain how we’ll ever know if it’s the hazel twig vibrating or you. Calm down and show me a steady pair of hands. That’s better! I’ll come with you and get you started. Here’s your marker.” Hermione scraped a line in the mud with the heel of her boot. “I see our handsome young architect has designed his own dowsing implement! Do you see? He’s abandoned his parallel rods and brought along that steel contraption he was describing to us. I wonder if he’s taken out a patent. Oh, look—he’s off already! Now, here’s a challenge, Doris! Let’s see if your honest-to-goodness hazel twig can outdo him!”

THE FORKED STEEL and the forked hazel moved along methodically at a slow walking pace, advancing towards each other from opposite sides of the tide-smoothed mud flats. The wands were held stretched out in front of the two dowsers in hands that grasped lightly, waiting for the inexplicable—but always shattering—upward tug or the sideways swivel.

After an hour, nothing more exciting than a metal-studded dog collar, a two bob piece and an ounce of rusty straight pins from the clothing factory upstream had surfaced. They’d been washed clean of the sticky black mud in a bucket of water thoughtfully hauled up from the river by Joel. Jack Chesterton, whose wand had located the pieces, was encouraged. “There, you see! I tuned my gadget to metal receptivity! And it seems to be working.” He looked with sympathy at Doris’s hazel twig and shook his head. “Not much point using what is essentially a water-divining device on a riverbank, is there?”