Flat tire

Not long ago I bought new tires for my car. They were worn out, spare tire too didn't look too good. But now it seems that we have a traitor in our midst- someone is sneaking in and vandalizing our cars. The first target being my car- releasing air from the tires. Revenge is sweet! It does not make sense that just one of the tires is always empty, the very same tire. But before accusing the gardener or cleaner or neighbor for it, I will investigate.