I think I am on level 20 or so. the guards keep coming out and wrecking everything I build. I'm supposed to have Frankenstein scare them away but where is he? I don't see him anywhere

I suggest you watch a YouTube video walkthrough of the game. You can find level 20 here. From there, you should be able to find other levels of the game.

Tsavorite, I've played this one several times. Make sure you don't clear the last obstacle before the guards and they won't come out. You will have to build the laboratory before Frankenstein can help you. At the end you will need to clear those last obstacles and make Frankenstein run like the dickens! Just don't let the guards out until you have to.

That all sounds like very good advice, Drac! Thank you.

I'm actually playing the game right now trying to get 3 stars on every level... just one more to go!