Perseus approaches the three Gorgons. They are all sound asleep. However, Perseus does not know which Gorgon in Medusa. So, Athena came to his aid and told him which one is Medusa. This is where Perseus is seeking the perilous 'heart' of the mission.
While the Gorgons are still asleep, he sneaks up by Medusa and cuts off her head with Hermes' sword. The two other Gorgons wake up soon after Perseus slays Medusa. This is where Perseus is confronted with the final, major conflict.
After slaying Medusa, he puts her head in the magic wallet to carry her head (which isn't in here because there was no wallet picture). The two other Gorgons begin to chase him after he begins to depart, however they cannot find him because of the cap of invisibility he has on (which again wasn't able to be put in). Perseus has received the reward of the head of Medusa.