The future of an entire people depended upon it.

And upon him.

Keenly aware of the pain Atlas had felt of old, Myrddin squinted against the downpour to study the profile of the hill rising up from the flatlands. The wind whipped through the crowns of mature trees at the summit, lashing them with brutal fury. As they drew closer, he spotted several white-water cataracts where rainwater poured off the hillcrest, surging and spilling its way down the steep, bramble-covered slopes.

It gave him an idea.

"I want to get right to the top," he said over the sound of rain and wind.

King Cadorius of Dumnonia grimaced, while the younger Melwas of Glastenning, in whose territory Caer-Badonicus actually lay, turned to him in visible dismay. "Now? In this driving downpour?"

"Aye, now. We'll be fighting the Saxons up there in conditions just as bad."

Covianna Nim, as bedraggled and mud-splashed as the rest of them, frowned. "I doubt we'll get the horses up that, not in this muck. That's a good thirty- or forty-degree slope and if ever there was a road to the summit, it's long since grown over and vanished."

Myrddin chuckled, which startled Cadorius and Melwas into staring. Accustomed to the limitations of most men's minds—and particularly those of kings, several of whom he had tutored personally—he explained with the same patience a mother reserves for her child: "The fact that there is no road works in our favor, for the Saxons will have just as hard a time reaching the crest as we will. Even without the nasty surprises I have in mind."

They did, indeed, have to leave the horses behind. Slogging their way through mud, through freshets of runoff that cut eroding gullies into the hillside, past wild brambles and outcroppings of native bedrock that scraped the hands and left the footing slick and treacherous beneath their feet, they climbed steadily toward the storm-lashed clouds. Panting, pausing to rest now and again, they finally scaled the summit, standing beneath a towering oak for protection from the wind-whipped gusts of rain.

Clumps of mistletoe, the "Druids' weed," had shaken loose from the oak's boughs, littering the ground with dark green leaves and clusters of tiny white berries, along with larger limbs snapped off by the storm. Blocks of stone lay piled haphazardly where work had already begun on the refortification, work interrupted by the rain. That, alone, would have to change. They didn't have time to wait on niceties like cooperative weather.

The view from the summit was impressive. Myrddin squinted against the rain, shielding his eyes with one hand while absently pulling his sodden cloak tighter around his shivering frame. Pacing off the distances, he walked the ancient walls, surveying the entire hilltop, while the king of Dumnonia and Melwas trailed along in his wake. Covianna remained huddled beneath the oaks, shivering and trying to stay out of the wind.

"We'll want circumvallations," Myrddin said at length, "several layers of them, right around the summit." He pointed, then knelt to retrieve a small branch, sketching what he intended in the mud, using his cloak to protect the muddy drawing as best he could. "My suggestion is five walls, at a minimum, arrayed like this, and we'll need shelters for a good-sized armed force to hold out against siege. Barracks, arms rooms, privies, stables for horses and livestock, pens for chickens and goats, shelters for womenfolk and children, for they'll need shelter behind strong walls when the Saxons come marching from the southeast, else they'll repeat Penrith on a grander scale."

"We'll need to dig wells," Cadorius muttered, "to support that number of people."

"Aye, and cisterns for rainwater, as well."

"There won't be room for cisterns," Melwas protested, squatting beside Myrddin's mud map and using a finger to sketch in the outlines of the buildings Myrddin had just enumerated.

Myrddin chuckled. "Ah, you're thinking in terms only of the summit. There'll be plenty of room. It's why I want five walls, not just the one or two you generally find with hill forts like this one. Look you, now, we'll build the five circumvallations like the labyrinth of Glastenning Tor, a maze of walls, with stone-lined cisterns between and gutters cut across the entire eighteen acres of the summit, feeding the rainwater into them, so none is wasted."

Melwas gaped. "You can't be serious? No one could build such a complicated structure in the time we have!"

"Nonsense," Myrddin snorted. "Haven't you read your Gallic Commentaries? Caesar's legions could have done it in a week, if not less."

The young king of Glastenning tried to find his voice, mouth working like a fish drowning in air. "But—"

"He's right," Cadorius cut in. "Remember, we'll have more than the farmers of Glastenning to help with the quarrying and the digging. Half the fighting strength of Britain is on its way here, with a fair percentage of them close enough to Badonicus, we should have a sizeable work force by tomorrow's sunset. We may not have the equal of Roman engineers, but we've plenty of strong backs and this is a brilliant defense plan." He tapped the muddy sketch, which rainwater was spattering into oblivion. "We could hold this hill for weeks, if need be, provided we can lay in the foodstuffs as quickly as we lay in the walls and cisterns and put up the shelters."

Myrddin nodded. "That, too, will be critical. The cataphracti and infantry due to join us will be certain to bring their own baggage trains with them, as even the greenest commanding officer knows an army of the size needed here cannot scavenge off the surrounding countryside as their only source of victuals. They'll have a sizeable store of grain and smoked meats with them, never doubt that. It's our job to be sure we've places to store it before the Saxons reach us.

"It's certain as sunrise the Saxons will cut any supply lines to Caer-Badonicus, the moment they arrive. It's a holding action we'll be fighting, distracting and keeping the Saxons bottled up here, goading them into trying to take this fortress, while the armies of the midlands and the north rush southward to join us. Without that fighting strength of the north, we'll never drive them back, so we must take great care to hold out until they can reach us—and make damned sure the Saxons don't scatter and ravage the countryside the way Cutha ravaged Penrith."

Melwas was still frowning down at the disintegrating mud map. "Why so many cisterns, though? With eighteen acres to provide runoff, surely so many won't be necessary? That's a lot of wall you're talking about, a lot of water, thousands of hogsheads, I'd say."

Emrys Myrddin grinned. "Indeed, you show a fine grasp of the mathematics. It's fortunate for us that the season's been one of the rainiest in memory. Come, let me show you something," Myrddin said, leading them back to the edge of the hill, where workmen had begun repairs to the old fortress wall. They had to squint into the teeth of the wind and shelter their eyes with upraised hands against the slashing rain. "If you were going to besiege this hill, would you put your tents here?" he gestured at the steep, rain-slashed slope. "In the brunt of the wind and rain? Or"—he led them across the summit to the opposite slope, where the wind and rain pummeled their backs—"would you pitch your tents here, in the lee of the hill?"

The lee side of Caer-Badonicus still suffered the effects of wind and rain, but the storm did not rattle so fiercely through the scrub here, nor did the rain fall with such brutal, wind-flung force. Myrddin spoke above the howl of the wind at their backs. "With this kind of weather to contend with—and it shows no sign of clearing up—the Saxons will have to cope with the same conditions we're fighting right now. They'll throw up a ring of men all the way around Caer-Badonicus, don't mistake that, but for any lengthy siege, even a day or two's worth of attacks, they'll want the bulk of their army out of the wind, particularly their sleeping tents. And that slope is the only place they can get it." He pointed downward. "So we prepare a little surprise for them."