"Looking ghastly as Lady Macbeth in the sleep-walking scene"

Macbeth is a tragedy by William Shakespeare, in which Macbeth and his wife are driven by greed for power to kill the sleeping king, Duncan, and many others who lie between them and the throne.  Whilst Macbeth commits the initial murder, Lady Macbeth returns to remove the bloody dagger from the corpse and later descends slowly into a guilty madness.  In a famous scene, a doctor and lady in waiting watch her sleepwalking, washing her hands obsessively in the belief that they are still stained and scented with blood.