After bowing towards his opponent, Walter took a stance, waiting for the moment Lupin became to cast his spell. He of course knew Lionel Lupin from work but didn't know him so much on a personal level. Not surprising as they weren't in the same class unlikely to have the same friends. It didn't bother Walter, being an Auror he had more advantages than a typical working class gentleman and he enjoyed his work too much to worry about the trivialities of being in a lower class than many he worked with.

As soon as Lupin twitched his wand, Walter cast his own spell, this time a silent casting of the paralyzing spell. One's opponent can't complete their spell if their body was as rigid as stone.

Marlena Scamander