The basic premise of The Late Nancy Irving is solid and genuinely creepy. An American professional golfer is kidnapped and awakens in some weird and posh medical clinic. Initially believing she is there due to an automobile accident, she begins to fathom that things are not what they seem, and something sinister is afoot. All the makings of a classic bit of horror are in place, but unfortunately don't quite come together.
As other reviewers have pointed out, the actress playing the lead role of Nancy (Cristina Raines) just isn't very compelling in the role. She's adequate in the pre-clinic scenes of the episode, but isn't able to carry the episode once she's had her "accident." The scenes of paranoia and suspicion fall a bit flat.
In a similar vein, "Mr. Big" (no spoilers) in the story is also a little "meh." Suitably evil, but not very menacing. It might have been better to keep him almost entirely hidden but for the necessary medical scenes (again, no spoilers).
On a more positive note, the supporting cast are generally quite good. Mick Ford is exceptional as fellow "patient" Tony Graham, and SPACE:1999 alums Tony Anholt and the always reliable Zienia Merton give solid performances as Dr. Marquis and Nurse Lee Parquet. There's a nice bit of depth to the two characters, blending in a bit of grey with the black and white of what is going on in the clinic.
Some people might not enjoy the deliberate pacing of the plot, which I thought worked well in slowly building tension. Most would probably agree that the ending is a little too neat and pat to be effective. The intent was probably to distinguish between the truly evil and the folks who did evil because they felt they had to, but it is an emotional letdown.
6.6/10.