The power of silence.
Corazon gets a call from Doflamingo saying that he has info on the Ope Ope no Mi. Some pirates found the fruit and are selling it to the Marines for a huge price, and Doflamingo plans to steal the fruit and have Corazon eat it, and Corazon can then heal Law. After the call with Doflamingo, Corazon is ecstatic, but he knows that Doflamingo is probably suspicious of him, and he also knows that Doflamingo wants Corazon to eat the fruit so Corazon can be sacrificed to give Doflamingo immortality. Corazon also can't eat the fruit because he already has a Devil Fruit power. So Corazon's plan is to steal the fruit before Doflamingo can and have Law eat the fruit. Being a spy of the Marines, Corazon calls Sengoku and gets details of the exchange, and also informs Sengoku of Doflamingo's plans. Corazon plans to use the Marines to take out Doflamingo while he steals the fruit for Law.
Three weeks later, Corazon and Law sneak onto the island where the exchange is going to happen. Law's condition has deteriorated, and so Corazon goes into action on his own. Using his Devil Fruit powers of silence, Corazon sneaks into the mansion where the pirates are staying and steals the Ope Ope no Mi. Corazon is overjoyed, but he trips and falls down a snowy slope after running out the castle and is caught by pirates who are guarding the perimeter.
Doflamingo calling Corazon about the Ope Ope is what I thought would happen. Corazon has things all planned out, playing off the Marines to take care of Doflamingo, but of course the best laid plans can go awry. Corazon's power is useful for stealth since people can't hear him, but his own clumsiness cost him in this chapter. Since we know the Donquixote family survived this encounter and was not wiped out by the Marines, we know Doflamingo probably had some other plans. Doflamingo was suspicious of Corazon anyways, and probably will make the attempt to steal the fruit.. maybe even when Corazon was captured. Looks like this flashback is coming to its conclusion.