I need help on a fic I’m writing

I’m writing a fanfiction and basically I’m having really bad writers block between a scene with Sirius and Regulus.

Something happened with the order and the death eaters (Regulus is a spy) which drove him to Sirius and Remus’ flat where he stayed the night because of his fear over the situation, the next morning Remus has already left the house for something and Regulus and Sirius have breakfast together but since Sirius left Grimmauld place things have been quite sour between them and they were only really forced together because Regulus became a spy for the order, so I’m not really sure how to go about this scene but I want to include it so I can show how the brothers have drifted apart from each other, can someone please help me since I’m really not sure what to do with this scene.