A robot is accidentally created with only a primitive brain. On the one hand, this means that it can break the First Law. On the other, it means it has the ability to truly learn—among other things.
I don’t like this story very much.
It’s intended to show Susan Calvin as a “mommy,” which is not a side of her personality I really find all that interesting to begin with. The real problem, however, is that it’s inconsistent with what we see of Susan Calvin elsewhere. “Liar!,” too, shows a side of Calvin we otherwise never get to see. This is a strength in “Liar!," however, because we are also given the reason why we never see it elsewhere. Calvin nowhere else shows her romantic side because it only brought her humiliation and pain, and because she burns it out of her soul at the story’s end.
In this case, we’re told that we otherwise don’t see Susan Calvin’s maternal side because she otherwise doesn’t have a robot baby. That seems somehow trivial and forced. You mean she could never build one? She has all the resources of U.S. Robots and Mechanical Men at her disposal, she almost certainly has the clout to get an experimental program underway—but she passively waits for the opportunity to present itself? Or does she understand herself so badly that she doesn’t realize that she wants a baby until one is given to her?
The possibility of a robot accidentally breaking the First Law is also rather more significant than its presence in this single story would indicate—and as a solution to US Robots’ inability to find engineers ("Advertise the danger!” says Calvin) is less than convincing. Companies like Apple, Microsoft, Google, Blizzard, Pixar—none of them have trouble finding recruits. After all, you’re at the cutting edge of technology, and you get to play with really cool toys. Asimov does raise this issue in the story, but it remains only half-convincing. In fairness, he wasn’t what we would call today a “geek,” and although he loved science, he never really had a passion for technology. He just never realized how much fun some people have playing with fancy gadgets, especially if they get paid to do it.
“Lenny” rather feels like the point of departure was, “Let’s see Susan Calvin play mother,” and it never got very far beyond that. It’s almost a shaggy dog story and exists solely to set up the final line.