Mark Slate sauntered in with a mob of giggling youths and girls soon after two o'clock. There was still a policeman on duty at the gate but he was deep in conversation with a tanned man who was wearing a fisherman's cap. Canned music blared from a juke-box somewhere in the middle of the sideshows and there was a lot of shouting and laughter competing with the cries of the barkers, the snap of rifles from the target booths, and the screaming of teenagers in a miniature hall of mirrors.

Children darted and tumbled between the knots of people gathering outside the kiosks.

Slate was heading, as unobtrusively as possible, for April's caravan. She had left it unlocked so that he could sit there, unseen and unheard, and talk to her over their Communicators while she made a reconnaissance of Sir Gerald Wright's big house on the cliff top beyond the Tor. The booth was being looked after by Sara, the equestrienne, who seemed to have taken a fancy to the girl from U.N.C.L.E. and had at once offered to deputize for her when April had pleaded urgent family business in Truro.

He threaded his way past a group of swarthy country boys crowded around a red-faced man in a tight brown suit who seemed to be knocking all the coconuts from their stands, and wandered up towards the canvas immensity of the Big Top. The sewn panels, battened down but bellying slightly in the wind, were drying out from grey to a bleached white.

In the aisle between the two rows of trailers, all was quiet: the fairground sound-effects were muted to a distant cacophony of three different jukeboxes playing different tunes with, a little nearer, an overlay of maniac laughter relayed from a tape loop in one of the "novelty" booths.

By the caravan in which April was staying, he paused to check that nobody was in sight, and then trod purposefully up the short ladder and went inside. Through the window above the narrow bunk bed, he gazed out over the cascade of slate roofs spilling down the valley to the harbour with its tangle of swaying masts. Somewhere along the wind-swept coastguard path which clung to the cliffs beyond, April was tramping towards Sir Gerald's house. Experimentally, he pulled the Communicator from his pocket, drew out its telescopic aerial and thumbed the call button.

The girl's immediate answer took him by surprise. "Channel open," she said; "and don't think I don't envy you, sitting there in my nice warm trailer while I'm up here in the teeth of a gale! Thank goodness I wore my thickest trousers and a sheepskin coat!"

"I only half expected a reply, as a matter of fact," said Slate. "I fancied you might not yet be far enough away from the madding crowd to talk. You must have made good time. Where are you?"

"Just rounding the corner of the headland below the Tor, where the cliffs dip down to Tregunda Cove. The Wrights keep a small boat there, I believe. A few more yards, and I shall be out of sight of Porthallow and in sight of their house up above the cove."

Involuntarily, the agent raised his eyes and stared once more out of the window. At this distance, even had he known where to look, a human figure would be indistinguishable against the great sweep of the Tor; it was hard enough to pick out the path to the old coastguard station, charting its sinuous course across the moorland with an occasional patch of fuchsia or briar or valerian showing dark against the Cornish heath. Yet somewhere on that jagged skyline was the owner of the melodious voice which was now proceeding from the pen-shaped instrument in his hand.

"What exactly are your plans, April?" he asked. "I'd like to know the form so that I can keep in touch mentally, as it were, if for some reason you have to make short, cryptic comments later — or if you can't come through at all, for that matter."

"All my comments are cryptic." The girl's voice had a hint of mockery in it. "And they'll certainly be short if my breath has to cope with climbing against this wind much longer! But, so far as I know, my aim is to stray from this straight and anything-but-narrow path as soon as I'm within reasonable distance of chez-Wright..."

"Straying from paths when he's around seems an easy task, from what I hear!" Mark observed.

"... and then to try and strike up an acquaintance with him by wandering onto his property and — as they say — engaging him in light conversation. I understand from spies in the circus that he customarily spends Saturday afternoons at home… and that his wife usually goes into Helston shopping at the same time."

"Okay. On your own pretty head be it! When can I expect to hear from you?"

"Give me a half hour. I should be approaching the property then, and I can give you a clearer idea of what's what. At the moment, all I can say is that those coastguards must have had feet of iron!" April sounded more breathless than ever as she picked her way along the rocky track.

Mark glanced at his watch, peered through the window to check that all was clear, and slipped out of the caravan. It seemed a little colder. He looked up at the sky and saw that the sunlight was now filtering through an immensely high gauze of cirrus which some stratospheric wind had teased out from the west.

The sideshows were more crowded still and the youth of Porthallow, red of face and long of hair, were thronging the two small arcades of pinball machines, laughing boisterously and indulging in ritual horseplay with the linked-arm duos and trios of girls. Ephraim Bosustow, a false grin scything his face, was acting as barker outside the sham gypsy caravan in which his wife consulted her crystal ball, and the middle brother — Mark had never heard his christian name — was twirling his waxed moustache at the clients in the shooting gallery. The biggest crowd of all was encircling the Bingo stall, where the widow of the late Harry Bosustow chanted the traditional couplets as she raked in the revenue that she was in due course going to conceal.

Slate smiled at Sara Bosustow behind the counter of the Serpentine souvenir booth and strolled towards the gate. Really, he thought, apart from the absence of someone pestering the clients to have their photographs taken, the circus was going about its daily business as though the blackmailer had never existed...

He was a few yards from the gate when somebody hailed him. He swung round. Superintendent Curnow, blue eyes twinkling, was talking to the man on duty.

"Hallo, there, Mr. Slate," the policeman called. "What are you doing up here, eh? Soaking up a bit of our local colour or trying to make your hotel expenses at the Bingo stall?"

"Taking an afternoon off, if you must know," the agent grinned. He walked over and shook hands. "How are your enquiries going? May we, the public, expect an early arrest?"

Curnow's expressive face darkened. "I'm not too sure of that," he said, "and that's the truth. We can't make up our minds whether the two murders are connected or not. On the one hand, there are things about the manner of them, the particular kind of callousness involved, that make me think they are; on the other hand, despite the fact that both victims worked here, there seems little doubt that there is nothing motive-wise to connect them... As a matter of fact, I'm on my way to Harry Bosustow's caravan now to collect all his negatives. We received an anonymous tip-off today that there might be something there — and while we don't normally act on anonymous letters, we have to explore every avenue we can in a murder case, don't we?"

"How do you mean 'something there'?" Mark asked. "Haven't you gone over the caravan? — If you don't mind my asking, that is."