This one is all about Shinwell. But at least it isn't about Watson trying to convince Shinwell of anything.
A gang member is murdered and Shinwell is a suspect. His prints are on the gun—or will be once the prints are run. But as it turns out Shinwell is actually an FBI informant? Except the agent he reports to isn't authorized to run informants so he refuses to help Shinwell because that would get himself in trouble?
Um, yeah, okay. Whatever.
Long story short (spoiler follows), the FBI agent and a couple cronies were the one to kill the gang member who, as it turned out, was also an informant and was putting said FBI agent at risk. But when Watson confronts the agent, he chooses to blow his own brains out rather than admit to everything. Which leaves Shinwell still in the lurch as the gun goes to be processed.
But Holmes does Shinwell a solid by pulling a few strings that allow him to get access to the gun and wipe the prints from it. So, you know, nice tidy finish there.
Can we be done with Shinwell now? And done with Watson trying to help stray criminals or whatever it is she's doing? Because it's totally not interesting and detracts from the show. She's interesting when trying to help Holmes. But Holmes helping people (Alfredo) and Watson helping other people (Shinwell) = not interesting, just annoying. The focus really needs to be on Holmes and Watson, their bond and them working together. That's the core strength here.