Is your spouse carrying on an extracurricular fling, or is it something you're just imagining? If your hunch is right and your mate really is involved with someone else, count on your lover to leave some clues.

"There are always signs," says Marcella Bakur Weiner, Ph.D., a relationship expert with a private psychology practice in Manhattan and Brooklyn, N.Y. "Nobody accomplishes a perfect cover-up," she adds. You can catch the Casanova ... if you know the tip-offs to adultery.

Relationship Reality Check

If your partner is two-timing, expect some of the clues to be emotional ones. According to Weiner, co-author with private investigator Raymond Green of 180 Telltale Signs Mates Are Cheating and How to Catch Them (New Horizon Press, 2002), your suspicions should be spiked if your mate:

• Pays you more attention than ever, or buys you presents ("guilt gifts") — especially early on in the infidelity.
• Picks more fights than usual, and is consistently moody, inconsiderate and critical, but doesn't want to talk about it.
• Isn't saying "I love you" anymore and no longer shows affection or has much interest in sex. (Or, after all these years, your partner brings new tricks to the bedroom for you to try.)
• Chooses to spend more time than ever with friends or at work — or claims to be doing so — rather than with family, and responds with delay to your cell phone messages.
• Seems to feel guilty when you do something nice (your mate is betraying you, and here you are treating him or her like gold).
• Responds defensively to your normal, everyday inquires, e.g., "Why are you always checking up on me?"
• Accuses you of cheating from out of the blue.

Make No Mistake

Your gut often tells you there's something gone awry. "Women have a kind of intuition to identify behavior that's even a bit unusual," Weiner says — but you can't be sure without more indisputable proof. To collect the evidence, Weiner says to be sneaky if need be, suggesting you check pockets, listen to phone messages, and even take a close look at credit card statements.

Experts say these additional hints can help catch a drifter:

• Some bills aren't coming to your house anymore — your spouse has likely diverted them to a work e-mail or P.O. box so credit card and phone charges won't give the affair away.
• Your significant other is going through cash much more quickly than usual, or withdrawing money from a strange location (check any ATM receipts you can find).
• Excessive mileage is appearing on the car's odometer — your mate says s/he's just going to work and back home, but that's not a 42-mile round trip!
• Your spouse has new tastes in music — used to hate country, but now can't stop two-stepping? — or is working out and placing more emphasis on clothes and general appearance.