When we first meet Aramis he is angry at D’Artagnan for inadvertently exposing his (Aramis’s) mistress. There is no choice but for the two to fight a duel.
Their duel is interrupted by the arrival Cardinal’s Guards. Aramis helps in fighting them off and then befriend D’Artagnan.
When helping to recover the diamond studs, Aramis is wounded in an ambush. He stops at a hotel to recuperate.
D’Artagnan later finds him about to take holy vows. D’Artagnan realizes that this turn to religion is due to not having heard from his mistress in several days. He produces a letter from the woman in question, and Aramis forgets all about joining the church.
Aramis and his friends head back to Paris. They receive word that they have to outfit themselves for war.
Aramis’s mistress sends him a small fortune.
Aramis bears witness at Milady’s trial.
He refuses the commission when D’Artagnan asks. He is going to join the church.