Case Zero may just be a short prequel, but it is a fun refresher and introduction to the upcoming sequel.
In this installation the player takes control of Chuck Greene three years following the events of the first game, as he travels cross-country with his daughter. Like any little girl she hates getting shots, but she is not just like any little girl anymore. She has been bitten, and now if she does not get an injection of Zombrex every twelve hours she will complete the transformation from living to walking dead. Too bad someone has just stolen their truck, along with Chuck's stash of Zombrex, marooning them in a town that is far less empty than it initially appears to be.
This prequel acts as both an introduction to the upcoming game and a reminder of the fun gameplay of the first. In this standalone story Chuck is given a list of different objectives that can be completed before the clock runs out later that night. Technically there is very little actually required to do and the player can choose which tasks to spend their time trying to complete. If you simply just want to swing away to your hearts content then there are plenty of zombies littered around town to heap tons of aggression on, and just as many items to vary up the means towards bloody mayhem. On the simplest level almost any object can be used when fighting for your life, from skull crushing heavy-duty wrenches, limb dissecting chainsaws, even paper cut producing newspapers; however, something new to consider is that many items around the world can be combined at workbenches in order to create something that will dole out more damage (to them) and merriment (to you). This does not mean that just anything can be duct taped together, but even the small amount of combos in this prequel improves the level of glee received from attacking zombies exponentially. You would not think that adding nails to a propane tank would make lobbing this weapon around any more satisfying, but you would be wrong.
The game may only be a few hours long, but this also makes the need to spend time wisely all the more prominent. On a first play through the player might have to tensely make the tough choices as to help every survivor Chuck comes across, where as on the other hand you can greedily just do what is necessary to make sure that Chuck and his daughter make it through this day alive. In actuality a combination of the two is completely possible, but it helps to have the previous knowledge of where special items and survivors are located before starting out.
Because of this, as well as the list of different achievements and the numerous endings that can be reached depending on your actions, there are plenty of reasons to replay Case Zero for the fans of the series and those new to taking on hoards of zombies at once. And though the prequel is not required playing, just think of it as the stretching before a race because you are not going to want to cramp up during the full-length game. That is how the zombies get you.