When it premiered in 2015, the spinoff prequel Better Call Saul looked poised to be the lighter, funnier cousin to Breaking Bad—and there was very little in the show’s early run that indicated anything different. Jimmy McGill (Bob Odenkirk)—the fast-talking, movie-quoting, morally dubious lawyer who eventually rechristens himself Saul Goodman—was always going to inspire more laughter than the milquetoast suburbanism or the smug menace of Walter White.

But over three seasons, the sunnier, goofier qualities of Better Call Saul’s protagonist have also earned the audience’s sympathies and lowered our defenses. And now that the audience has fully invested in Jimmy, Better Call Saul can stick the knife in.

(Spoilers for the first three seasons of Better Call Saul below.)

The fourth season of Better Call Saul picks up almost immediately after where the season three finale left off, when Jimmy’s brother Chuck killed himself. The suicide was sparked, in large part, by his inability to overcome a psychological condition that manifested itself as an extreme sensitivity to electricity, and season four will follow the rest of the characters as they grapple with their feelings of guilt and complicity in Chuck’s tragic end.

I won’t spoil anything about Jimmy’s exact reaction to the news of his brother’s death, except to say it’s one of the more realistic depictions of grief I’ve seen on television. But if we imagine Better Call Saul and Breaking Bad as one long continuum on the journey from "Slippin’" Jimmy McGill to the unrepentantly criminal Saul Goodman, it’s clear that Chuck’s death marks a sudden and dramatic pivot point toward the latter.

And as Jimmy continues to flirt with the line between cleverness and criminality, the tone of Better Call Saul changes. In season one, we were on Jimmy’s side, laughing at his inventiveness and brazenness as he bootstrapped his way into the legal community of Albuquerque. As time has passed, the clever schemes are still there—but the fun has been sucked right out of them, for both the audience and for Jimmy. It’s all there in the season four poster, which depicts Jimmy as a kind of Pagliacci—holding a strained, grinning mask over his face to disguise his inner misery.

Unlike Breaking Bad—which began with an extremely sympathetic protagonist and gradually revealed his inner monstrousness—Better Call Saul began with a protagonist we knew to be an irredeemable slimeball and revealed the earnest, wounded heart behind the goofy commercials and tacky suits. But like Breaking Bad, Better Call Saul has also introduced plenty of thorny complications into its seemingly reductive moral structure. Saul has argued, sometimes persuasively, that Jimmy really is incapable of playing it straight—which leads, inevitably, to terrible consequences for anyone who gambles on him.

And that’s the big question Better Call Saul has left to answer. Did Chuck sabotage his brother’s big chance at a happy, functional life as a law-abiding pillar of society? Or was he just the only person who knew Jimmy well enough to recognize that Jimmy was always going to cut corners and self-sabotage, no matter how much it hurt the people around him?

Even with Chuck gone, this is not an abstract question. Kim Wexler (Rhea Seehorn)—Jimmy’s romantic and business partner, and the show’s best character—has wagered everything she has, both personally and professionally, on Jimmy’s inherent goodness. But if she had a crystal ball (or a Netflix account with Breaking Bad all queued up), Kim might hedge her bets a little harder. Whether it was inevitable or a self-fulfilling prophecy, Chuck’s skepticism about his brother turns out to be right.