How do I get the Dr. Henry Walton (Indiana Jones) achievement in Kingdom Rush: Frontiers?

You can "help Indiana find the secret passage" on stage 11 Temple of Sagra. Indiana will appear on the roof of the right hand side building. Quickly push the tiles on the wall in this order: Second tile, First tile, then Third tile. This will open the secret passage and crush the bed of Parasyte eggs. Don't mess up the order of the tiles, or you will release the little facehuggers, and no one wants to deal with them.