Parasitic drain on car battery?

Please help. I own a 1997 ford escort europe MK something, and I have this strange problem:

Whenever I leave battery connected overnight, it ends up empty. The thing is, if I disconnect it and connect it before use, it works and never discharges. The alternator gives it proper juice, everything is perfect.

Now, the fun part. WHen I measure parasitic drain, it doesn't exceed 20mA.

Is it possible some relay switches on at night and takes huge load from the battery? Or where would you look for a problem. The battery itself seems very fit.

It could be a faulty diode in the alternator. It would still charge while running but immediately start discharging the battery when the car is turned off. It's a pain to do but you could start pulling fuses while observing the meter til you find the circuit that causing the drain.

Guys, shouldn't there be a drain in order to discharge my battery? Is there any other way? Because the measured drain is 20mA, which should be fine. Can you tell me how to check contacts from and to alternator step by step?

Do the fuse check, and check for the obvious: faulty connections like bad insulation, rusty ground connections, loose connections, etc