In his cramped quarters, he had shifted from one position to another until it seemed as if every muscle was aching, but he kept to his post.
At length, after what seemed to be a very long wait, voices at the door again made him keenly alert.
Four figures appeared.
Gently pushing aside a branch, he was able to get a good view of the group. One was tall and slim, dressed in a gray suit and wore a straw hat.
But Bob's glance quickly left this man to centre on two figures who had a strangely familiar look.
"Where can I have seen them before?" he mused.
His eyes eagerly roved from one to the other, as the group approached the gate.
One of them presently turned. His profile was sharply outlined against the sunlit ground.
Like a flash, Bob recalled where he had seen the two before. It was on the little steamboat which they had encountered when passing through the lock.