spoiler alert ---
this is a bit graphic.
in the first 15 minutes of the show, they pick up where they left off last year. there's a quarantien because of the mysterious illness. the whole hospital -- except for those affected by the mystery disease -- is going to be evacualted. Susan and Luka take a patient up to the roof to board a medivac helicopter. Romano takes a patient up to the roof for the same reason. Luka and Romano argue over who should use the copter. Romano chases after a piece of paper from his patient and walks into the blades of the helicopter and loses an arm. no one can use the heliicopter now, and another one can't land. Luka takes Romano downstairs to treat him in the now empty ER -- other doctors are called in to help. Luka's patient is taken downstairs to an ambulance, and Susan is left alone on the roof with Romano's patient.