The writing in this is on point. Both characters have a well established dynamic and... well, character. The conversation felt organic while also subtly detailing what kind of world this takes place in. It allowed the situation to be very easily understood despite jumping in right in the middle of things. It also gave me a very good sense of what Garth and Sarah's journey has been like and how they get along.
The mood is also established super well. The ambient music and dark environments really establish a sense of palpable atmosphere. Add on some very solid descriptions of the environment, and you have a very well presented scene!
My one gripe is how the dialogue choices are handled. Each choice doesn't really lead to much in the way of different dialogue, and it sometimes feels like the conversation is written largely around one of the options. For instance, take the moment where Garth reveals that he's out of tablets. When Sarah asks why he didn't mention it earlier, the "I didn't know either" option fits into the conversation really organically. She responds that she thinks/knows that response is BS and accuses Garth of not trusting her. If you select "I didn't want you to worry," however, we get that exact same exchange, and it just doesn't feel right.
Another example is the speculation on the hatch marks. Whichever response you go with, be it dead kids or how many people were left, you get the response of "Well, that's morbid" and go on. The first option just has an extra line from Sarah. I feel that these different dialogue options could have led to more interesting individual exchanges with their own pieces of information that could add texture to the world, the characters' relationship, their attitudes, or anything else. It feels like a missed opportunity to me, even if some of the options are quite similar in message.
Still, this is very good for what it is, and a solid example of what a game that's a scene long can look like!