Although both Normal Sirius and Current Sirius would likely be chagrined to hear it, Regulus was pretty certain that his brother had just become the greatest threat to his life in the world. If Sirius managed to remember their talk the other day while he was under Imperius, it was a tossup whether he'd come after Regulus himself or go straight to Bellatrix, and neither option was all that good; of all the horrible things Sirius had been saying, both to Regulus and to other people, the very worst so far was that he was proud of Regulus for taking the Mark; Regulus had nearly gone to have a lie-down after that.
Thank God for Walburga, really; she'd learned of Sirius's return and immediately declared it to be a trick and Bellatrix to be a moron. Likely the two sides of the family would be having it out shortly, but as of when Regulus stopped home to change and got caught up in his mother's shrieking rants, there was no plan to officially reinstate Sirius as heir.
Lord. He could just kill Bellatrix for getting them all into this mess.
He would have bowed out of visiting Sirius, pleading a headache that he actually did have, if not for Edgar Bones. Sirius's friends were counting on Regulus for information, and so was Sirius himself, somewhere in there.
Two days ago, he never would have pegged Sirius as the Black brother in need of rescuing.
So Regulus arrived at Lestrange Manor shortly after supper, dressed in plain black robes and hoping his misery came across as tiredness from work; knocking at the door, he waited to be let in, fidgeting uncomfortably. He really hated coming here, and at this moment, he would have much preferred being home listening to Walburga scream.