"How you gonna explode it'?" Ham questioned.

"It explodes itself, due to chemical reactions, about four minutes after the two compounds are mingled."

They huddled in the corner farthest from the vault door. Doc employed his mighty bronze form to shield Ham — although Ham did not realize it at the time, so great was his nervous tension.

"It's about time for the blast!" Doc breathed swiftly. "Open your mouth wide to equalize the pressure on either side of your eardrums, so there'll be less likelihood of them being ruptured."

Ham barely had time to comply.

Wh-a-a-m! Compressing air smashed them against the solid steel with stunning force. It crowded their eyeballs inward. It seemed to tear the flesh from their bones.

So terrific was the explosion that Ham was reduced to senselessness.

Doc Savage, huge and bronze and apparently affected not at all by the concussion, flashed to the heavy steel door. It was still shut. But the hard metal was ruptured about the lock. He shoved.

The door opened about a foot and stuck. But that was enough. Doc carried the unconscious Ham outside, thence through two vacant chambers.

Ham revived after several minutes in a large, bare room — the lobby of a former bank.

Pedestrians moved on the street outside the unwashed plate-glass windows. One of these chanced to look in. He was a portly man with spats and a cane, smoking a cigar. No doubt he had heard the blast.

Doc Savage rushed Ham to a side door. It was locked. The lock came out of the hard wood like an ear of corn out of its shuck, when Doc exerted a little of his tremendous strength.

A taxi driver at a stand in the street heard the lock tear out. He glanced around. He was just in time to see the two men climbing into his hack.

The driver bellowed for a cop.

The cop came. He did not know Doc Savage by sight. He pinched both Doc and Ham. Doc did not put up an argument. This was the quickest way of getting clothes. The cop was tough, and swore a lot.

At the police station, the captain in charge insisted on stripping to his underwear so that Doc would be properly clad.

And the cursing cop got a lecture from his superior that would make him remember the giant bronze man the rest of his life. He would also have gotten suspended a month without pay if Doc hadn't interceded.

"Anyway, begorra, yez had better learn to know some of the big men in this town by sight!" the captain warned his cop.

TWENTY MINUTES later, Doc Savage stood on the wharf, appraising Captain Chauncey McClusky's under-the-polar-ice submarine.

The thing looked like a razor-backed cigar of steel. The hull was fitted with lengthwise runners resembling railway rails. As a matter of fact, these actually were such rails, converted to the purpose of ice runners. They were supposed to enable the underseas craft to slide along beneath the arctic ice pack.

A wireless aerial, collapsible, was set up for action. There was a steel rod of a bowsprit ramming out in front, the size of a telegraph pole. The rudder and propellers were protected by a steel cage intended to keep out ice cakes.

Doc liked the looks of this latest of polar-exploring vehicles. He stepped aboard.

A man shoved his head out of the main hatch amidships. All this man needed to make him a walrus was a pair of two-foot tusks. Doc had always believed Monk the homeliest human creation. It was a toss-up between Monk and this man.

The man squeezed out of the hatch. He would tip a pair of scales at three hundred pounds, if he'd budge them at an ounce.

"What the blazes do you want aboard here, matey?" the man demanded.

His voice was a roar that frightened roosting gulls off floatsam in the middle of the bay.

"I'm hunting Captain Chauncey McCluskey," Doc announced.

"You've found him!" roared the walrus. "An' if yer a dinged landlubber just wantin' a look at this bloody hooker, you can take shore leave right now! I been pestered to death by cranks since that piece come out in the papers this mornin'!"

Doc didn't bat an eye. He rather liked to deal with a man who got down to business and said what he thought.

"Let's look your vessel over," he suggested.

The walrus blew noisily through his mustache. "Mean to say you're interested in buyin' a share in this expedition?"

"Exactly — if your craft meets my needs."

"Come below, matey," rumbled Captain McCluskey. "I'll show ye her innards."

They looked at her innards for an hour and a half. They came back on deck.

Doc was satisfied.

"It will take approximately two hundred and fifty thousand dollars to see you through," he said. "I will put up the sum — on one condition."

Captain McCluskey blew through his walrus mustache and eyed Doc as if wondering whether the bronze man had that much money.

The walrus would have been surprised if he had known the true extent of Doc's wealth. For Doc had at his command one of the most fabulous treasure troves in existence — a vast cavern stored with the wealth of the ancient Mayan nation. This was located in a lost canyon, the Valley of the Vanished, in the remote recesses of Central America. Survivors of the ancient Mayan civilization, living isolated from the rest of the world, kept Doc supplied with mule trains of gold whenever he needed it.

"What's the one condition?" McCluskey rumbled.

"The expedition must be entirely in my hands the first two months," Doc explained. "Within that length of time, I shall visit a certain remote spot in the arctic regions, and secure the thing I am going after."

CAPTAIN MCCLUSKEY was surprised. "The thing you're goin' after — what d'you mean, matey?"

"I'm afraid you'll have to swallow your curiosity on that point, captain. The object of our quest will be disclosed when we arrive, and not before. I can assure you, though, that it does not involve breaking the law in any way."

The walrus considered deeply. "All right, matey. I'll sail two months under your sealed orders. But, strike me pink, if yer breakin' the law, I'll throw ye into the brig the minute I finds ye out."

"Fair enough."

"Cap'n McCluskey is as honest a swab as ever sailed the ocean," the walrus continued his roaring. "I've saved me money many a long year to bank enough to build the Helldiver. The good lads in me crew have done the same. We want to do somethin' to leave our mark in the world, so we'll be remembered after we're in Davy Jones's locker.

"This explorin' v'yage under the pole is our bid for fame, matey. It means a lot to us. We ain't gonna be throwed off our course this late in the game. Maybe ye don't understand our feelin's, but that's the way it is."

"Naturally, my project will not interfere with your goal of sailing under the north pole," Doc replied. "And you may rest assured we shall make no effort to share in the glory of your accomplishment. I shall not permit my name to be mentioned, either as partial backer, or as having accompanied you."

The walrus man seemed deeply moved.

"Yer a generous man, matey," he mumbled. "But one other point, we'd better clar up."

"What's that?"

"The hearty lads in me crew," chuckled Captain McCluskey. "Them swabs ain't sissies, matey. They're good men. They've sailed in naval submarines aplenty in their time. But they're hard as iron an' a little rough in their ways. You said you'd bring five of your own mates along. That's all right. But if they ain't got hair on their chests, my crew is liable to haze 'em around some."