At a Manhattan teaching hospital, the life of Dr. Bock (George C. Scott), the Chief of Medicine, is in disarray: his wife has left him, his children don't talk to him, and his once-beloved teaching hospital is falling apart.
The hospital is dealing with the sudden deaths of two doctors and a nurse. These are attributed to coincidental or unavoidable failures to provide accurate treatment.
At the same time, administrators must deal with a protest against the hospital's annexation of an adjacent and decrepit apartment building. The annexation is to be used for a drug rehabilitation center; the building's current occupants demand that the hospital find them replacement housing before the building is demolished despite the building being condemned sometime before.
As Dr. Bock complains of impotence and has thoughts of suicide, he falls for Barbara Drummond (Diana Rigg), a patient's daughter who came with her father from Mexico for his treatment. This temporarily gives Dr. Bock something to live for after Barbara confronts him.
The deaths are discovered to have been initiated by Barbara's father (Barnard Hughes), as retribution for the "inhumanity" of modern medical treatment. Drummond's victims would have been saved if they'd received prompt, appropriate treatmentâbut they didn't. Dr. Bock and Barbara use a final, accidental death of a doctor at the hospital to cover Drummond's tracks. Barbara then takes her father back to JFK airport to escape back to Mexico, leaving Dr. Bock at his insistence to try and organize the chaotic Hospital.

Question: How did Dr Bock and Barbara covered up the deaths in the hospital?
Answer: They used an accidental death of a  doctor to covered Drummond tracks.
Alternative answer: a final accidental death of a docter.