Understanding a "state variable" RC-active filter
Jack, Op Amp actually works like, let's say 'an amplifier' when we have feedback in the Negative input - just like you did. I don't know what is the frequency of your input signal, so, what it looks to is that your 10nF capacitor is acting as an 'open circuit' for the OpAmp in the middle. 

Well, I mentioned the feedback in the negative input. In your case, however, the OpAmp in the middle looks like it's working without a feedback (because of the high impedance of the 10nF capacitor). OpAmp works like a differential amplifier, when there is no feedback. The differential amplifier will amplify the difference between the signals applied at the (+) and (-) entries. In your case, as the (+) is connected to the ground, the output from OpAmp1 will always be compared to 0. 

I don't know if I made myself clear. To conclude, it looks like your circuit will behave like this for low frequencies. In case you start using a bit high frequency, you will certainly notice a different behavior - and not a square wave in the output. 

Let me know in case you want some more explanation!