Possible Clues:

• Harbour suspicions of rodent infestation
• Be suspicious when corrupt master holds everyone back
• Suspect one can spot a deserter under the bridge?
• Suspect trickery and calumny at absorbing libel case
• Suspect something's amiss, with master criminal holding everything back!
• Get a sense something's up
• Suspect something's amiss
• Awfully smart woman brought in? Be suspicious
• Suspect lets alarm go off
• Be suspicious when old West Indian captain tucks into salmon?