Sleeping Dogs: Year of the Snake is a DLC (download content) for Sleeping Dogs. It is set after the game's conclusion when the city prepares for the upcoming New Year celebrations. Wei Shen has returned to regular police work, but he is demoted to beat cop work. However, during his rounds he discovers a plot by a strange cult to bomb the celebrations and the game follows Wei's efforts to foil their plan.
The DLC is started separately from the main menu and assumes Wei unlocked most of the upgrades during the main storyline, e.g. he has a full health bar. He has also learned two new abilities: when grabbing an enemy, Wei can either use an taser (which puts the enemy out of the fight for a short period of time depending on how long the button was pressed) or simply arrest him (only works when health is low enough). The main missions involve the same gameplay elements as the main game, e.g. car chases, melee combat or shootouts. There are also a number of side missions available which usually either involve short small-scope police tasks like catching a thief or the new gameplay mechanic of driving rigged cars in the ocean before the bomb explodes.
Beating missions unlocks new vehicles, outfits and reports on the New Year celebrations (there is no upgrade system); beating the DLC unlocks assets to use in the main game. Wei has a bit of money to his disposal to buy buffs or transportation by taxi, but does not earn additional funds.