Fred followed the line of George's wand and it took a moment, but he recognized the blood for what it was, too, and his mouth set into a serious, tight line that was rarely seen on either twin.
He took point ahead of George, walking down the short hallway, following the bloodtrail back to where it was quite obviously seeping underneath the closed study door...
Fred wasn't one for nerves, though, and he reached and pushed the door open without waiting.