It's not yet clear whether it was a mistake or a strategic decision, but tonight's episode of AMC's The Walking Dead is available for purchase, and to watch streaming, right now via Google Play.
You have to buy the full season--that's $27.99 in standard definition or $42.99 in HD--in order to get the early access, but buying Season Four of The Walking Dead will indeed give you immediate access to the first episode, titled "30 Days Without an Accident," which airs tonight at 9 p.m. EST.
Again, this may turn out to be an error on Google's part and if so, might be "fixed" by tonight. But at present, the episode is available. Our recommendation, if you can, is to run like little Carl over to the Google Play store if you want to see it early.