A Marked Man

Alex:  "Did you write those things?"
Amy:  "What things?"
Alex:  "The markings on my arms."
Amy:  "Where?"

{Alex turns on the lamp, examines his arms and hands, and rubs his face.}

Alex:  "It must have rubbed off."
Amy:  "What did it say?"
Alex:  "It was the wrong thing."

{Alex turns off lamp, looks at clock, and groans.}

Alex:  "Ugh!  It's 12:30."