Why was he suddenly so sad?

After sitting around in his car for a long time, Mark drove back to the hotel and returned to his suite. Inside, he found Peter pacing around like an ant on a hot plate. Seeing that Mark was back, Peter quickly walked over to him and asked, "Where have you been? Why did you go out alone? If something happens..."

Mark sat on the sofa.

He was exhausted, but still, he maintained impeccable posture. He was never one to slouch no matter how awful he felt.

He casually picked up a throw pillow and was about to put it behind his back, but then, he caught a whiff of its smell.