- I saw Jane and David whispering in the hallway the other day. I wonder what it was about.
- I don't know. I saw them meeting in the canteen too.
- It's very strange. What can they be up to?
- Ooooh, I wonder if it's about the new manager who started last week. I heard a rumour that Jane and David want to get him fired.
- Ah, you might be on to something there! I'll see if I can find out more.
Note that despite checking various online sites, I can't work out if we use "on to" or "onto"! It's not something I often write down.