“I’ll bring her back.”  Barry laid kindly hands on the old man’s shoulders which had seemed suddenly to stoop as though beneath a burden.  “Don’t worry.  I expect she’s only had some trifling mishap.  Burst a tyre probably and is walking back.”

St. John’s look of acute anxiety relaxed a little.

“I hope so,” he muttered, “I hope so.”

A servant opened the door.

“The car’s waiting, sir.”

“Good.”  Barry strode into the hall, Mallory following him.

“Barry, I must go with you,” he said hoarsely.

In the blaze of the electric light the two men looked hard into each other’s faces.  Then Barry nodded.

“Right.  I’ll leave the chauffeur behind and drive myself.  We must have plenty of room at the back in case Nan’s hurt.”  He paused, then held out his hand.  “I’m damned sorry, old man.”

“I suppose Kitty told you?”

“Yes.  She told me.”

“I think I’m rather glad you know,” said Peter simply.

Then, hurrying into their coats, the two men ran out to the car and a moment later they were tearing along the road, their headlights blazing like angry stars beneath the calm, sweet light of the moon overhead.

The old dame who kept the keys of the castle rose from her supper as the honk, honk of a motor-horn broke on her startled ears.  People didn’t come to visit the castle at this time of night!  But the purr of the engine outside her cottage, and the long beams of light flung seawards by the headlights, brought her quickly to the door.

“We want a key—­for the castle,” shouted Barry, while to expedite matters Peter sprang out of the car and went to the floor of the cottage.

“The key!” he cried out.

She extended her hand, thinking he had brought one back.

“Ah, I knew I’d missed one,” she said.  She shook a lean forefinger at him reprovingly:  “So ’twas you run off with it!  I’m obliged to you for bringing it again, sir.  I couldn’t rightly remember whether ’twas a young lady or gentleman who’d had it.  There’s so many comes for a key and—­”

“It was a lady.  She’s up there now, we think.  And I want another key to get in with.  She may have been taken ill.”

Peter’s curt explanation stemmed her ready stream of talk abruptly.  Snatching the key which she took down from a peg on the wall he returned to the car with it.  Barry was still sitting behind the steering wheel.  He bent forward, as Peter approached.

“You go,” he said, with a bluntness that masked an infinite understanding.  “There’s the brandy flask”—­bringing it out of a side pocket.  “If you want help, blow this hooter.”  He had detached one of the horns from the car.  “If not—­well, I shall just wait here till you come back.”

CHAPTER XVI

SACRED TROTH

The tide was at its full when Peter began the ascent to King Arthur’s Castle—­the sea a vast stretch of quivering silver fringed with a mist of flying spray.  In the strange, sharp lights and shadows cast by the round moon overhead, the great crags of the promontory jutted out like the turrets of some ancient fortress—­blackly etched against the tender, irresolute blue of the evening sky.