The first half of the scenario is a perfectly fine little series of runs (yes, more than one). It doesn't require the runners to be based out of LA, and in fact assumes they're in Seattle at the start. They get hired to protect some "authentic" movie props of questionable legality and high black market value (like real Red Samurai armor and gauss rifles) during the production of an over-the-top action movie (basically Dawn of the Artifacts - nice in-joke there). After foiling a heist by another runner team, they're invited to LA to keep doing the job for the rest of the shoot. Once there, they get hired on a real run to find out who's been blackmailing mega-star pop singer Christy Daee, and to recover the compromising material they're threatening to expose.

If the book ended here, and cost half what it does, it would be a very good adventure. The Horizon part comes next, though, and it's not as good. They actually explain this plot to the GM at the very start, but it only really comes into play now.

Horizon has been developing something they call a "Life Management Guide", which is basically a kind of expert system that lives in your commlink and drives you to be a "better person". It does this both through targeted advertising (by spamming you with adds for healthy foods, gym memberships, and so on), and by blocking AR objects related to behaviors it considers "negative": smoking, drinking, violence, et cetera. This includes even blocking out bad news from your feeds. It's also a virus, spreading stealthily through P2.0 connections and taking over any AR-based software in users' commlinks.

Before the run begins, they had been beta-testing this in a specific P2.0 user population, and the thing unintentionally spreads to Christy Daee's commlink. To avoid bad PR, the Horizon sub-corp in charge of testing quickly patches her copy of the software to activate a poorly-documented "U56" flag, which they think just deactivates the subliminal conditioning. It does do that, but also marks the user in question as "Undesirable", and leaves an extensive data trail. This interacts badly with the subliminal conditioning already imposed on the original test population of ex-cons and criminals, turning it effectively into a "Target for Assassination" flag. Whoops! This flag also spreads virally along with LMG to anyone the original "undesirable" connects with on P2.0. Which, after the runners help Ms. Daee out, includes them. Double Whoops! After Ms. Daee, her manager and a few other artists she was in contact with get killed, the runners are tasked with finding the killers, while also being targeted by them.

This scenario sounds exciting on paper, and can likely be worked on a bit to really become so, but the setup for it is really contrived. All of the events related to it are railroaded, from forcing the runners to accept P2.0 subscriptions and keep them on at all times so they can be infected by Daee's LMG, to the sequence of events that leads them to the killers. They must get ambushed at a certain point, and only then can they find out about the LMG and U56, and only then can they go after the killers, who at this point have become "Undesirable" themselves from all the murdering and started targeting each other, meaning the case practically solves itself. And after everything is dealt with, and the runners are paid, they have their P2.0 subscriptions revoked by the movie studio and sent back home because they've become "too popular" and thus "useless as runners".

As for the LMG itself, when Horizon finds out about all of the above, it sends the code to another company for "phase two development", which probably means "weaponizaton". It's implied, but not outright stated, that this was the intention all along.

In closing, while the adventure gives some peace of mind to those who thought Horizon was "too clean", it does so in a way that's a bit too railroady for my tastes, and would require some re-tooling. The first half of it doesn't have anything to do with the Horizon plot, but is just fine by itself - there's a lot more plot there than there was in the first half of On the Run, so even if your PCs skip the second half by never turning on P2.0 and leaving town before the murders start, you'll still get some value from your money.