Vader does not take his focus off Plagueis. Not once that name is mentioned - if anything, his attention, his focus, sharpens like a nexus teeth. Sidious had made him sound like a legend, not someone he personally knew.

Fine.

"My apologies Darth Plagueis," Kneeling, he bent his head in a bow, "I-" he what, didn't recognize him? "I've only been told of you."