You are a convicted criminal living in a grim post-apocalyptic future in which the Earth's surface has been contaminated by a virus so deadly that it killed five billion people thus forcing the surviving population to live underground.
In this scenario you may be forced to "volunteer" on a mission to the surface in a barren Philadelphia. You will need to collect bugs and return your specimens to the underground. You may also be asked to allow scientists to send you on dangerous missions to the past to collect information concerning the virus. Which may enable the human race to return to the surface.
The time machine may be incredibly inaccurate and may cause you to be sent to the wrong time. If this should occur you may be regarded as mentally unstable and committed to an asylum.
When you finally arrive in the correct time period you should kidnap your psychiatrist from the previous time. Be warned that she may develop feelings of pity for you and eventually fall in love with you as she begins to believe the signs that the world is heading for disaster.