Or rather it would have been done if turning to see that the way was clear behind him, Louis had not discovered a second watcher, who from a spot on the edge of the island was marking his movements with grim attention.

This watcher was Basterga.

Moreover the glance which apprised Louis of this showed him that the scholar's face was as black as thunder.
Then, if the gods looked down that day upon any mortal with pity, they must have looked down on this young man; who was a coward.

At the one end of the bridge, Claude, with an ugly weapon and a face to match! At the other, Basterga, with a black brow and Heaven alone could say how much knowledge of his treachery! The scholar could not know of the loss of the phial, indeed, for it was clear that he had just returned to the city by the St.Gervais gate.

But that he soon would know of it, that he knew something already, that he had been a witness to the colloquy with the Syndic--this was certain.
At any rate Louis thought so, and his knees trembled under him.