Regulus gestured an 'alright, later' at Lily's request and after she left the room he rolled his eyes but he followed.

Lily was a few paces ahead of him, leaving a gap. And Regulus almost ran to catch up when an undead suddenly stumbled out of a room and split the difference between them.

"Lily-!" he shouted a warning, in case more would come through the room. And he deftly raised his wand and dispatch the undead the way he preferred, with a good old Reducto.

He caught up to Lily before the dust settled.

"See, I'm already getting your back."