When a fourteen-year-old girl is reported missing, and her stabbed body is found on the heath, Tennison is determined to solve this last case before she retires. Complicating matters is the fact that her father is admitted to hospital and is discovered to have inoperable cancer and given little time to live.
As the case deepens and suspects are found and discarded, Jane's drinking reaches the point where she is threatened with being removed from the case and pushed out the door early. It would be an ignoble ending to a distinguished career, and perhaps it's the thought of seeing it all go for naught that pushes her into attending Alcoholics Anonymous for the first time. Or perhaps it's the fact that she gets to see herself through the eyes of another for a change.
In the course of the investigation, she becomes friendly with the deceased girl's close friend April, and sees her reflection in the eyes of the younger woman. As the case winds itself down to its sordid and bitter conclusion, Jane has begun the process of making peace with herself, and although retirement will be a long tough haul for her, she at least has something to work on — herself.
Long before she was famous for being a Calendar Girl or the Queen of England, Helen Mirren created the role of DSI Jane Tennison. Her performance throughout Prime Suspect has always been exemplary, but like all the best performers, she has held something back for the last hurrah.
There's a fine art to television acting involving subtlety and restraint. To be able to create a character as complex as DSI Jane Tennison, and then to bring her to life as completely as Mirren manages to do is an accomplishment that very few will ever be able to equal. In "The Final Act" we watch Mirren take Tennison to the very edge of the abyss of self-destruction and draw herself back from the precipice before falling.
There are none of the histrionics that we would see from a lesser actor or production, no scenes of flying booze bottles or tearful confessions. Instead we watch the character trying to act like nothing untoward is happening. However, that's not very easy to carry off when she suffers from a blackout and forgets the call that notifies her about the girl going missing.