To be honest, Christopher did not know Hermione Granger at all. Sure, he knew of her- after all, she was one of the best and brightest of Hogwarts, and a muggle-born to boot, which did not sit well with a lot of people in house. This will be the first they speak to each other face to face, and Christopher cannot help but foresee an immediate future with lots of awkwardness. Merlin, he hoped there won't be too many of those. He also hoped that this will be the first step to getting some answers since Miss Granger was the the only eyewitness. Christopher had already gone to the authorities, but only to be turned away like all other family and friends of other victims.
He may appear to be incredibly levelheaded on the outside-
"Uh," Christopher began intelligently, trying desperately not to fidget, "Sorry. Is this is a bad time?" He made a thumb gesture behind him, as if turning to leave, "If you're busy-" The former Slytherin paused briefly, thoughts falling into place as he straightened up his posture, and finished politely, "But I would like to speak with you, if you have the time, about my wife's disappearance."