Kevin couldn't tell from the noises who was on the first floor, but he knew that wasn't where the action was. His targets were upstairs, on his sister's bedroom, and he had a long trip to do.
He ran towards the stairs as fast as his one and a half inch body could take him, realizing how something that would take him two steps at normal size now basically took him almost a minute at a decent speed, and thinking that it would have been nice to have some clothes because even if he was tiny, it still felt a bit weird running across the house naked like that.
Looking up at the dozen of stairs he would have to climb Kevin sighed with frustration, feeling he was stupid for not drinking the vial upstairs in his room. Fortunately for him the carpet runner made things a lot easier, and even if he felt his body getting dirty with those minuscule particles of dirt that a normal sized human would miss, it meant he could just gently pull on the threads and push himself up instead of doing some serious climbing that would likely leave him exhausted.
It still took Kevin a good 5 minutes or so to conquer the stairs, because it was hard to gain any rhythm going after what basically was a series of little climbs followed by little walks as he went through each of the steps. But finally he was there, he could hear the murmurs and laughter coming from his sister's room and he could take a nice walk towards Lucy's door while he thought about how exactly to prank them.
Should he just show up and scare them? The initial reaction would be priceless, but after that things could be scary for him instead. Maybe he could climb on Lucy's drawer or nightstand and move things around pretending to be a ghost? Kevin wondered if he was strong enough to pull it off, or how bad things could be if he was caught. As he got near Lucy's door and noticed he was just the right size to squeeze through the gap under it Kevin wondered if his best course of action would be to stay hidden and wait until a better idea came up or a right time to pull out a prank appeared, maybe whatever the girls were talking about gave him an opportunity to strike.
What happens next?