Then Jack gave Harrison the whole story.  He omitted nothing that the boys considered of importance, even showing Harrison the map.  At the conclusion of the recital Harrison looked serious.

“Well, boys,” he said at length, “you’ve stumbled onto what seems to be a reality, but I always considered it a myth.  For years the report has been circulated that there was such a treasure and this man Wyckoff and Lopez claimed to be blood descendants of the officer who buried it.  The name on that map would seem to bear them out.  But tonight or tomorrow night will be the only time you’ll have to get at the treasure for another year, if the whole tale is true.”

“How’s that?” breathlessly asked the boys.

“I can’t explain the whole thing, for I never attempted to memorize details, always believing the story a fairy tale, but as I recall it, the moon and tide must both be just right—­something like the moon is tonight and the tide will be in a short time—­and then the ground around the chest softens up and the chest comes to the surface for the rightful heir to reach out and get it.”

“If there’s anything at all in that,” asserted Jack, “I’ll bet the thing lays in a bed of quicksand.  When the tide is just right it softens up and boils.  Then any solid substance may be thrown up to the surface.  Maybe someone has seen a piece of log or some driftwood at some such time and that’s the way the treasure story started.”

“But I have the map,” declared Harry excitedly.  “What do you make of that?  You’ll have to go some to explain that.”

“I guess that’s so,” sheepishly admitted Jack.  “I forgot that.”

“Until tonight,” stated Harrison, “I never had much faith in the story, but this map as a climax to other things is convincing.”

Rowdy, who had been lying on a berth with Arnold, now slipped to the floor.  His whole body became tense and rigid while the hairs on his back rose on end.  A low, menacing growl issued in subdued notes from his throat.  His attitude was threatening.

“Watch the dog,” whispered Jack.  “Look at him.”

“Someone’s coming,” announced Arnold.  “He does that only when he gets near someone who’s a sneak or pirate or something.”

“Goodness, I’m glad I’m not a pirate,” declared Harrison.

“Get a leash on him,” ordered Jack.  “He’s been shot once tonight and that’s enough.  Get your guns unlimbered, boys.”

“I’ll keep a lookout on the water,” volunteered Frank.

“And I’ll watch the wharf,” said Tom.  “I wish, though,” he continued, “that the lights were off.  I could see better.”

“Turn the switch, Charley,” was Jack’s request.  “It’s at your hand there on the bulkhead.  It’s the middle one.”

“I see him,” whispered Tom.  “It looks like Wyckoff.”

“Slide the door open a crack,” Harry suggested, “and get the drop on him.  If he starts anything, shoot him in the legs!”