Lucius was running late. He had intended to get to Gringotts earlier in the day, but had run into an old acquaintance who happened to have come into an inheritance recently, an inheritance involving certain items in which Lucius was very interested. Namely, books about horcruxes.
His business concluded, Lucius was on the way out of the bank when he caught sight of a very familiar-looking man. Lucius paused, looking closer, thinking furiously. He knew all the living Blacks, knew their features and their mannerisms, and this man was quite clearly a Black. But who? An illegitimate son, perhaps, or--
Lucius' mind ground to a halt after realization struck. "Regulus," he murmured, genuinely shocked. Quickly throwing off his surprise, he strode up to the man. Eying him up and down, he added with a smirk, "You're looking... lively."