Telltale's The Walking Dead: Season 2 - Episode 1 will release on Steam on December 17th. If you pre-purchase the entire season you'll receive 10% off the listed price (which for the UK brings the price down from £18.99 to £17.09). It's not yet clear when the first episode will land on other platforms.
Season 2 has also received a brief synopsis:
"The Walking Dead: Season Two continues the story of Clementine, a young girl orphaned by the undead apocalypse. Left to fend for herself, she has been forced to learn how to survive in a world gone mad.
Many months have passed since the events seen in Season One of The Walking Dead, and Clementine is searching for safety. But what can an ordinary child do to stay alive when the living can be just as bad – and sometimes worse – than the dead? As Clementine, you will be tested by situations and dilemmas that will test your morals and your instinct for survival. Your decisions and actions will change the story around you, in this sequel to 2012’s Game of the Year."