It's after 6 p.m., a long, grueling day has come to an end. You stand in front of your apartment door, impatient to get home. As you insert the key into the lock, it stubbornly refuses to turn. You try again, and again, but nothing works: the key remains stuck. An exasperated sigh escapes you.

Charles, your roommate, comes in right behind you. You had a big row this morning, and the atmosphere between you has been icy ever since. Without a word, he glares at you and leans over to examine the stuck key.

"Did you call the plumber?" he finally asks, breaking the tense silence.

"Yes, he said he'd be here in an hour," you reply, without looking away from the door. The tension between you is palpable.