The plot was discovered before it was ripe, and all having been apprehended, were placed by Mago in the hands of Adherbal the praetor, to be conveyed to Carthage.
Adherbal, having put the conspirators on board a quinquereme, sent it in advance, because it sailed slower than a trireme, and followed himself at a moderate distance with eight triremes.

The quinquereme was just entering the strait, when Laelius, who had himself also sailed out of the harbour of Carteia in a quinquereme, followed by seven triremes, bore down upon Adherbal and his triremes, feeling assured that the trireme, when once caught in the rapid strait, would not be able to return against the opposing current.

The Carthaginian, alarmed by the suddenness of the affair, hesitated for some little time whether he should follow the trireme, or turn his prows against the enemy.

This very delay put it out of his power to decline an action, for they were now within a weapon's cast, and the enemy were bearing down upon him on all sides.

The current also had rendered it impossible to manage the ships.