The Pair of Blue Flip-Flops Behind the Door

In the corner of the entryway, there's a pair of worn-out, flat-soled blue rubber flip-flops. Ever since I was young, whenever I went out and returned home, the first thing I'd see upon opening the door was this pair of flip-flops neatly placed in the most visible spot in the shoe rack. Back then, I thought my dad was very organized, arranging even the house slippers like soldiers. Then one time, I was late due to overtime and got home well past midnight, dragging my tired body. The alley was dark, and the hallway was quiet. I quietly took out my keys to open the door. The living room lights were off, with only a faint glow emanating from the kitchen. I looked down, and the blue flip-flops were still placed by the door. Just as I was about to change my shoes, the gap in the bedroom door opened slightly. Dad, rubbing his eyes, peeked out from inside. Seeing it was me, he sighed in relief and said, "You're back? There's soup left on the table, drink it while it's hot." At that moment, I suddenly noticed that he was barefoot on the cold wooden floor. It turned out those flip-flops were never placed there beforehand. He was sitting in the living room, watching for any movement by the door. As soon as he heard my keys, he'd quickly arrange the flip-flops, then quietly retreat back into the room, pretending to have been asleep all along. Those seemingly natural orders were nothing more than someone silently keeping watch, paving the way for your safe return home.