“Don’t worry, old chap,” Gavin said to the growling collie.  “He’s had all he can carry, for one day.  He’s not going to follow us.  By this time, he’ll begin to realize, too, that his face is battered pretty much to a pulp, and that some of my body-smashes are flowering into bruises.  I pity him when he wakes up to-morrow.  He’ll be too stiff to move an inch, without grunting.  His pluck and his nerve are no match for his strength ....  Here we are!” he broke off, beginning to skirt the hither edge of the swamp.  “Unless all my dope is wrong, it ought to be somewhere close to this.”

He walked more slowly, his keen eyes busily probing the impenetrable face of the swamp.  He was practically at the very end of the beach.  In front, the mangroves ran out into the water, and in an unbroken line they extended far back to landward.

The shining dark leaves made a thick screen, shutting from view the interior of the swamp.  The reddish roots formed an equally impenetrable fence, two feet high, all along the edge.  It would have been easier to walk through a hedge of bayonets than to invade that barrier.

“Where mangroves grow, puppy,” exhorted Brice, “there is water.  Salt water, at that.  The water runs in far, here.  You can see that, by the depth of this mangrove forest.  At first glance, it looks like an impasse, doesn’t it?  And yet it isn’t.  Because—­”

He broke off, in his ruminative talk.  The collie, bored perhaps, by standing still so long, had at first turned seaward.  But, as a wavelet washed against his white forefeet, he drew back, annoyed, and began aimlessly to skirt the swamp, to landward.  Before he had traveled twenty yards, he vanished.

For a second or so, Gavin Brice stared stupidly at the phenomenon of the jungle-like wall of mangroves that had swallowed a seventy-pound dog.  Then his brow cleared, and a glint of eagerness came into his eye.  Almost running, he hurried to the spot where the dog had vanished.  Then he halted, and called softly: 

“Come, puppy!  Here!”

In immediate obedience to his call, the dog reappeared, at the swamp’s edge, wagging his plumy tail, glad to be summoned.  Before the collie could stir, Brice was at his side, taking sharp note of the direction from which the dog had just stepped out of the mangroves.

In front, the wall of leaves and branches still hung, seemingly impenetrable.  The chief difference between this spot and any on either side, was that the mangrove boughs had apparently been trained to hang so low that the roots were invisible.

Tentatively, Brice drew aside an armful of branches, just above the waiting dog.  And, as though he had pulled back a curtain, he found himself facing a well-defined path, cut through the tangled thicket of root and trunk and bough—­a path that wound out of sight in the dark recesses of the swamps.

Roots had been cleared away and patches of water filled with them and with earth.  Here and there a plank bridge spanned a gap of deeper water.  Altogether—­so far as Brice could judge in the fading light—­the path was an excellent bit of rustic engineering.  And it was hidden as cunningly from casual eyes as ever was a hermit thrush’s nest.