he screwed up his courage and knocked on the door , and when a young woman answered , and came out on the porch to look for her visitor , and was bewildered because she did n't see anyone there , charlie slipped past her , grabbed the vase , and was out the side door before she came back in , his heart pounding like a war drum , adrenaline sizzling through his veins like a hormonal tilt-a-whirl .