During all this time Cleopatra

During all this time Cleopatra and Ptolemy remained in the palace with
Caesar, both ostensibly co-operating with him in his councils and
measures for defending the city from Achillas. Cleopatra, of course, was
sincere and in earnest in this co-operation; but Ptolemy's adhesion to
the common cause was very little to be relied upon. Although, situated
as he was, he was compelled to seem to be on Caesar's side, he must have
secretly desired that Achillas should succeed and Caesar's plans be
overthrown. Pothinus was more active, though not less cautious in his
hostility to them. He opened secret communication with Achillas, sending
him information, from time to time, of what took place within the walls,
and of the arrangements made there for the defense of the city against
him, and gave him also directions how to proceed. He was very wary and
sagacious in all these movements, feigning all the time to be on Caesar's
side. He pretended to be very zealously employed in aiding Caesar to
secure more effectually the various points where attacks were to be
expected, and in maturing and completing the arrangements for defense.

But, notwithstanding all his cunning, he was detected in his double
dealing, and his career was suddenly brought to a close, before the
great final conflict came on. There was a barber in Caesar's household,
who, for some cause or other, began to suspect Pothinus; and, having
little else to do, he employed himself in watching the eunuch's
movements and reporting them to Caesar. Caesar directed the barber to
continue his observations. He did so; his suspicions were soon
confirmed, and at length a letter, which Pothinus had written to
Achillas, was intercepted and brought to Caesar. This furnished the
necessary proof of what they called his guilt, and Caesar ordered him to
be beheaded.