Possible Clues:

• Do a tense recitation?
• Name all forms of a verb
• Coupled prisoner and prison were worrying
• Do a grammar chore
• Recite verb forms
• Maybe go through mood changes of criminal: prison worried
• Recite a verb's forms
• Name all the forms of a verb
• State the various parts of a verb
• Lag worried about jail, go through forms of torture, perhaps?