Starts hilariously, with Glen ending up at a couple's place (Art and Cyndi) after a car accident, and Art convincing him to sleep with his wife. This looks like a trap of some sort, and even more when Art comes up to Glen's place announcing that Cyndi is pregnant.

But, everything is more complicated than that, A LOT more, and nothing is really what it seems. The narrative structure chosen allows for layers upon layers of lies to be peeled off as we slowly learn more about what really happened.

There are three separate but intertwining stories.

1) Glen, his relationship with Cyndi, and their time in the lab
2) Art selling his services to the wannabe senator
3) Shannon and the lab work

Once you see the big picture, the main point is Art's revolutionary [spoiler]hypnosis technique[/spoiler]. The title, Ultrasound leads you to believe that something is going on about weird pregnancies, Cyndi's, and the great introduction scene for Katie, where it appears that she is very pregnant without realizing it. But both actually are Art's work.
[spoiler]After quitting the research lab with his technique he tries to sell it for election purpose to senator Harris. As a first proof, he makes Katie, the senator's mistress, believe that she's not pregnant, and uses Cyndi, his assistant, and Glen, a random guy probably chosen because he's very receptive at a wedding where Art is performing, as future foster parents who will believe it is their own child by convincing them believe Cyndi is pregnant. Dr Conners, Art's ex partner, kidnap them to use them to reverse engineer Art's technique. Shannon is working there as she thinks it will be used as a cure for veterans, and rebels when she learns the applications will be military.[/spoiler]

But to get to this point, information is slowly distilled as we put the pieces together, that's really captivating throughout the story as there are several layers of lies or [spoiler]hypnosis[/spoiler] on most characters. Notably Glen, who Art [spoiler]convinced that Cyndi is pregnant, and Conners convinced that he's disabled. But it also turns out that the intro scene situation where he met Art and Cyndi didn't even happen either[/spoiler].

The ending situation is a little more blurry.
Shannon [spoiler]seems to have escaped, but did she ? It's not really clear whether the technique has been used on her or if she has just been lied to.[/spoiler]
Cyndi [spoiler]seems to be free of the influence, as she remembers how she really met Glen[/spoiler].
Glen [spoiler]is at least still under the influence of Art's wedding show, and free of the pregnancy and disabled legs lies, but he still believed to have met Art and Cyndi as a couple[/spoiler].
Art has a [spoiler]falling out with the senator, but he still appears on stage with him, weird as Katie apparently is out of his influence and know she's pregnant. Can only suppose that he used his technique on the senator. But then wouldn't Katie being aware be a danger for him too ?[/spoiler]

Great idea, great story, complex but not enough that you're lost, and each revelation makes sense as we learn bit by bit. Really a great job.