This article is from the Prophecies of Nostradamus FAQ, by firstname.lastname@example.org.
I p193 (cI-4)
The second-to-last pope instated after the assassination of the
current one will have a short reign. Due to political blunders and
mistakes he will pave the way for the final pope to be a tool of the
Antichrist. His reign is an omen of the final downfall of the church.
I p 196 (cII-36)
Before the Antichrist comes to full power it will appear that other
leaders are above him and in control of the power structure other
than him. In reality the Antichrist is using them as stepping stones
in his quest for world power. During this period he will have
traitorous cardinal working for him, spying on the second-to-last
pope. One of the cardinals will steal information from him and alter
the pope's personal correspondence, so that it has different
connotations. It will make the situation appear inordinately worse
than it is in reality, causing the pope to react inappropriately.
This way the populace will be more likely to see him as incompetent
and destabilize his authority, possibly by being assassinated. The
cardinal will be troubled by his betrayal because of the obvious
dissension it causes the Church, but he is allied with the Antichrist
and will rationalize away his backstabbing.