Hello. Signed up to play.
Here's my initial sketch. Agent [name to be determined later] is one of many sanctioned by the government to track and dispose parasitical beings that were accidentally released from top secret labs. These parasites must be stopped since their hosts never survive infection and to cover up the government's secret experiments and mishandling of the accident. The beings can only be effectively eliminated at the point where they are the weakest - when they emerge and shed their hosts bodies and still maintain their soft skin, easily penetrable by a toxin laced bullet.