At length, however, on rounding a corner, the travellers were startled by a sudden flash from the tower. They halted, Burton levelled his glasses, and declared that he saw two heads and pairs of shoulders projecting above the top. Other flashes followed, at intervals long or short.
"They are heliographing to the main body behind us," he said to Enderby, repeating the information in French to the Serb.
"Can they see us?" asked Enderby.
"They might perhaps if they looked, but they are gazing far beyond us, of course. We had better back a little, though."
They had, in fact, halted before the oxen had come completely into view from the tower, and by backing a few feet they were wholly concealed.
The three men held an anxious consultation. The tower was probably two miles ahead. To go on would involve discovery by the enemy. On the other hand, parties of Bulgarians might already be marching up the track behind them. It seemed that they were trapped.
"We had better wait a little," Burton concluded, "and see whether they leave the tower and go forward. In that case we might venture to proceed."
The signalling continued for some few minutes, then ceased. The men disappeared from the summit of the tower. Burton was on the point of suggesting that they should move on when he caught sight of a small figure flitting rapidly from rock to rock down the track towards them.
"It is the boy," he said, after a look through his glasses.
In a few minutes young Marco arrived, excited and breathless.