Stupidity: After the first session with Madame Arcati, she says good bye, then heads off to the front door, which is all wrong: She left her bike around the back, near the living-room door, the door with which she entered.
Stupidity: When Ruth goes to see Madame Arcati, after Elvira has arrived, the kettle on a gas two-burner hotplate is whistling, so Madame Arcati takes the whistle off the kettle and then the kettle off the hotplate and pours most of the water into a teapot, but, what is stupid is, she puts the kettle back onto the same burner without turning the gas off and in less than a minute the water is boiling its head off but they don't notice because the whistle is on the table and not where it is supposed to be, on the kettle.
