Take a spare to somewhere in the house where he/she rarely goes, and plug it into the phone jack. Unscrew and remove the mouthpiece (ahead of time) so that your sotto voce epithets will not give your sleuthing away. When you hear him/her shout “I’ve got it, honey” (cause you just know it’s him/her), go to your “war room,” and very carefully lift the receiver off the hook. Don’t be too gentle: wiggling the buttons will make a clickety sound on the line that will get you busted.

If you have a smart phone or a feature phone with a recorder, set the earpiece of the headset next to the microphone, and record the lovey-dovey ramblings for posterity. If the jig is up, and you have what you need, then no need to wait. Confront the louse with his/her toothbrush and an overnight bag, and send him/her out without his/her dessert. If it turns out, however, that the phone was his/her bowling buddy confirming Lane 6 this Thursday, whip up his/her favorite dessert, and serve it up with a smile.

Paint the transmitter (the baby/secret side) with the spray paint. Cover up the microphone hole before you paint so you don’t gum up the works, and don’t over-paint. You don’t want that thing to be stinking up the house. Go to the room where you think she’ll be making throaty sounds with her licentious Lothario, and cache the transmitter in a discrete location where she’s unlikely to look. Behind some books, or the couch, or if you’re really hapless, somewhere in the bedroom or bath. Power it up, and put a portable radio in the room turned down to about human-whisper-and-giggle level. Go into your man cave, and turn on the receiver. Can you hear the radio? If so, you’re ready to go. If not, make adjustments until you can hear the transmitter signal clearly. When that phone call comes, and she says “I have to get this. . . it’s work,” say, “Okay, honey, I’ll be in the man cave surfing the ‘Net for. . . " (You can say almost anything there: after she hears Okay, honey, I’ll be. . . , she’ll already have too much adrenaline pumping through her to hear you, anyway. ) Go to your room, turn on the monitor, power up your recorder (phone, tape, whatever you’ve got), and listen to what happens next. Should you hear what you fear, call her a taxi, and send Ruby Roundheels on a one-way ticket to town. Of course, if you hear “Okay, I’ll have that report by tomorrow, boss, and I. . . . wait, what’s this. . . a transmitter?,” you might want to take that taxi yourself. You’re going to be in hot water.

Check email. Another way he’ll schedule snogging sessions with that woman is to send send her emails or chat online. What if every email or conversation that your spouse sends online got mailed to you to read? Software called remote spy software records all of his or her emails, chats, instant messages, web sites visited and keystrokes and then automatically copies this recorded information to your email address. Unless your spouse is very careful, you can also pop onto his or her computer (or phone) when he or she is not around, and look at history, recent applications, and other breadcrumbs to follow the trail of the philandering fink. Maybe a little email planning for the next rendezvous with romance, or some online hot chat logs. The lout who is having the affair will quickly try to prevent you seeing emails through the use of passwords and saving the emails under different file names. To gain access initially, you may try using his typical passwords as a starting point. If that doesn’t work, a Google search will easily find specialized software that can hack passwords.

Honestly ask yourself why you don’t trust your spouse. Do you have any reason, real or imagined, to believe your spouse is, or has been, unfaithful? It doesn’t have to stand up to legal standards of proof, but do you have anything to go on beyond your feeling or hunch? It is not uncommon for a partner to self-convince that there is a case of spousal infidelity based merely on circumstances that have been molded into the evidence needed to justify one’s own feelings, beliefs, and insecurities. Just because he seems less interested in you doesn’t mean he’s cheating. Working late or going out with friends might mean only that. It’s also not uncommon for couples who have been together for a while to forget why they fell in love because everyday life is a grind and people get comfortable with time, taking one another for granted. Moreover, sometimes work addiction takes over, and your spouse really has become “wed to the job or start-up” and rarely thinks of spending time with you.

She’s not going to send emails from the home computer, or call from the home phone. She’s not going to claim to be working late and leave for a hotel rendezvous risking your calls going unanswered or being seen leaving work too early She will use normal routines and patterns that you are well used to and simply use that time to have the affair. A sexual affair doesn’t require much time or commitment. The two of them meet in the parking lot, hop into one car, head for “their room” at the Motel 9 for a half hour, and are back in time for shopping. She even comes home with purchases consistent with where they were supposed to be. So if you’re truly committed to finding the truth, do this:

Do your homework and make it look like you’re leaving town by sharing details of your trip, while you secretly plan a stay at a hotel just out of town. (If your spouse expects details of your trip, book them, get confirmations to share with your spouse, but cancel at the last hour and stay close to home. )

Follow your spouse (a rental is a good idea), but if you are prone to road rage or other rash acts, think twice about this one. If your spouse simply goes home, park down the street and watch.

If you need more time, call the morning you were scheduled to be home and apologize that you have to stay one more night.