Conversation so far:
What can you tell me about this?
After 35 years of loyal service, d'Artagnan resigns as lieutenant of the Musketeers as he perceives the young king Louis XIV as weak-willed.
Why would that make him resign?
CANNOTANSWER.
What happened next?
He resolves to aid the exiled Charles II to retake the throne of England, unaware that Athos is attempting the same.
How does he help Charles?
With their assistance Charles II is restored to the throne and d'Artagnan is rewarded richly.
What happened next?
In France, Cardinal Mazarin has died, leaving Louis to assume power with Jean-Baptiste Colbert as his finance minister.
How did he do once he was in power?
Colbert has an intense hatred for his superior the king's Superintendent of Finances, Nicolas Fouquet, and tries to bring about his fall.
Are there any other interesting aspects about this article?
He brings to the king's attention that Fouquet is fortifying his fief of Belle Ile secretly.
What did the king do?
Louis persuades d'Artagnan to re-enter his service, and tasks him to investigate Belle Ile, promising him a substantial salary and promotion to Captain of the King's Musketeers on his return.

Question: What did he find during his investigation?
Self-contained rewrite: What did d'Artagnan find during his investigation?