Deceit

Now free-to-play, Deceit is a multiperson FPS that challenges players not only to kill their enemies but figure out who their enemies actually are. You wake up in an asylum, one of six people. Two of you have been infected by a virus and are tasked with sabotaging the group. At times, the infected with transform into horrifying monsters, unleashing their full fury on their would-be comrades.

Deceit relies on clever map design and psychological manipulation to achieve its goal of presenting a shooter that's about more than just racking up a body count. Will you escape the asylum? Do you help your fellow inmates? Or are you just in it for yourself?