Just walked in on the babysitter… (weird)

I know this is every porn cliche, but this just happened an hour ago.

My wife works from home, but had to leave this afternoon for a conference out of town. She picked up her best friend's little sister (name and age redacted for obvious reasons) this afternoon to watch our 20-month-old son until I got home. I wrapped up work a little earlier than expected and headed home.

This girl has watched our son many times before, but this is the first time it's been in the afternoon and only I've been there. Michelle (my wife) had obviously discussed the plan with me earlier, and made arrangements for me to take her home after I got off work. I get home expecting to find them in the living room watching tv, but the house is silent. I figure they've gone for a walk in the neighborhood, but when I walk by the nursery, I see my son in his crib. I called out the babysitter's name and get no response.