As suggested by ME (because I like awkward things):
Part Two (Do-over)
Harry stood at the door to the prefects bathroom for a good two minutes, baffled and a tad irritated with Cedric (though, really, it was his own fault for waiting so long to take his advice) when the door opened with a puff of steam and someone careened into his invisible body.
"Cedric?" Harry asked before he realized he was still invisible.
"Who's there?" Cedric whipped his head back and forth warily, and Harry could see him groping for his wand in the bundle of clothes he carried.
"It's okay, it's just me!" Harry took off his cloak before Cedric did anything rash.
"Harry?"
"Yeah. Here to work out my clue." Harry glanced around.
"Oh. Well, hop to it, you're taking forever." Cedric smiled uncomfortably, and gave a little wave.
"See you in a bit."
"Yeah, you too." Harry's heart was still racing from the startle as he stepped into the grand bathroom and shut the door.