Empty third node

I'm using Resolve 9 Lite, and I'm admittedly a noob to this CC software, just downloaded today, in fact. I have run into a real puzzle -- when I add a third correction node, it's blank, and does nothing. If I add a fourth one after it, the fourth one works fine. What's going on with this?

Is it connected to the output?

See my example.

Yes it is.

See the stripes in the connected line from node 2 to 3? That one tells you it's transporting whatever mask or key from 2 to 3. Usually it's done for inverting a shape or key.

In this case, it doesn't look like you have made any shapes or keys, so node 3 doesn't have anything in it, because it's an inverse of a full image. If node 2 had a Power Window (or shape if you like), node 3 would effect the opposite of node 2.

Play with it, you'll get it soon.

OK, very interesting, thanks. I'm definitely going to play with it -- this program is addictive. Still wrapping my mind around node-based work, but the possibilities are astounding.