Doomsday Is Tomorrow

Other reviews have detailed the action and plot. I will add:

This is a war of wills against Jamie, in her most human form, versus a cold, ruthless AI driven computer.

If anything this episode is a fine example of the "computer out of control" sci-fi drama. More relevant now, as the speculative AI of the Alex 7000 has become a reality with AI becoming more of a societal influence than ever. And in this episode, the lag of ethics keeping up with technology is clearly shown.

Scary on the onset in 1977, but 48 years later all more so.

The power of Lindsay Wagner as an actress here is in full display; the range of human emotions is impeccable. The plot of Jamie navigating her own emotions and tempering them against her cold adversary is complex and so well done. A duel to the bitter end and well done.

Also, perhaps, one of the best science fiction "movies" ever - where characterizations of Jamie and Alex 7000 are the focus, with just enough FX as to move the color along as opposed to overwhelm. (On a par with Star Trek - the Ultimate Computer with the out of control AI powered M5)

(Of note, even the immense size of the research complex is plaisible, given the size of data centers now.)

I remember watching this episode - and Part 2 - with my entire family. Seven kids plus mom and dad. This episode has a simple but relevant plot - world peace through blackmail. As long as no country detonates another nuclear bomb, a "Doomsday device" will never go off. Add to that a nice homage to HAL the computer from "2001: A Space Odyssey" - ALEX the computer protects the Doomsday device. The banter between Jaime and Alex is what propels these two episodes, especially Part 2.

These episodes were so tense, my entire family barely breathed! When we found out it was a two-parter at the end, we all screamed at the TV.

When Part 2 aired a week later, we had Jiffy Pop popcorn all ready to go before the episode started. We again watched, hardly saying a word, it was that good!

I only wish they could have sustained this level of writing and production for about five years. This series deserved more like this.

This is extremely good sci-fi for TV and would easily be major feature film quality without changing much except improving only a few effects.

It uses the infamous soap sud machine of the 70s, but for a realistic purpose.

Jump scares are one of the most cliched tropes, but this episode pulls off a fantastic one in a 100% credible manner.

As another reviewer said, Wagner shows just how great an actor she is, carrying the bulk of the second half while interacting only with Alex's voiceovers.