Your Timeline tells you where and when to focus your attention to verify your partner's story of where your partner is going.
You can ask a friend to follow your partner, that's not known to your partner. (Your partner doesn't know them or their car.)
You could also rent a car for those times when you need to verify your partners where about's and keep it parked close by. Don't forget to wear a hat or some attire that won't look like you from a distance.
A car following another car can be tricky but here are some tips:
1) Never be directly right behind the subject vehicle. Try to keep at least one car between you & the subject vehicle. Not too far back that the subject vehicle makes a green light and you get a red light. ( If you do get a red light, turn right at the lights and make an immediate U-turn and turn right at lights and get behind the vehicle again.)
2) If possible and depending on the roadway your travelling on, stay in a different lane than the subject vehicle but don't get in a situation where you've both got a Red light and you rolling up right beside the subject vehicle. (in case you do you have your disguise.)
The other option would be to hire a Private Investigator to surveil your partner at the suspected time, from your Timeline/Log.
When hiring a Private Investigator you'll be asked to pay a retainer, about $1,000.
Based on their hourly rate which could be $85. an hour. This gets you a little over 11 hours of P.I. time..
Example: If your timeline suggests your partners going somewhere after work then you'd want to spend those hours watching your partner leave work and see where your partner goes and have the P.I. follow your partner home where he would break-off the surveillance and continue another day, until you run out of the retainer and your asked for another one.
Example: If you can never get a hold of your partner at lunch time, maybe you should see what your partner does at lunch time. If your partner works in a busy downtown area this would probably mean your partner will be on foot and would require the P.I. to be as well.
Maybe your partner goes to a motel/hotel at lunch time or always hangs out with the same person at lunch.
As I said before this is the most expensive way to solve the problem, but it will solve the problem.
There's still other ways to solve this problem of, not knowing what's going on.
Keep reading through the pages and see for yourself.