The Case of the Secret Safe

In the wee hours, a certain something in my house was thumping around and causing me distress. I went to investigate.

I unscrewed the air vent, which seemed to be secured tightly (probably not the source of the thumping).

I poked at the electrostatic air filter, which was a little loose (probably the source of the thumping).

But I had this feeling there was something more. 

With my pulse racing and my stomach somewhere in my throat, I tilted the filter toward me.

And this is what I saw:



That is a safe, with a handwritten note taped across the top. The note reads: "Safe is not locked. Pull top up by knob."

Many thoughts are flying through my head at this point. First, why would you give someone instructions on how to open your safe? Isn't that information usually private? My expectation would involve a combination, secret key, retina authentication... Have I just seen too many movies?  Second, I wonder what's in there! Ooooh! This could be a blog post!

My top three most plausible ideas are:

1. Donkey wheel that, when turned, will change the G Family's location in time and space.

2. Jimmy Hoffa.

Tied for 3. Thomas Crown's supplemental storage or a zombie head.

I have not opened the safe to confirm my guesses. What do you think could be in there? And, maybe more importantly, what do you think is?