Talk about a way to end a season. The fourth season of Dexter had the title character facing off against John Lithgow's superbly terrifying Trinity Killer, and at the end of the series' final episode, it appeared that Trinity had finally been put to rest. However, Trinity left a nasty surprise waiting for Dex when he returned home, discovering a dead Rita lying in the bathtub filled with blood (as was Trinity's frequent MO), while their son Harrison sits in a pool of blood crying, as reflects Dexter's own similar fate as a child. Rita was an incredibly important character because she helped normalise Dexter and promoted the prospect that he could, in fact, have a normal family life. With her gone, that was completely destroyed, and affected Dex throughout the rest of the show, as he came to realise that he did genuinely love Rita, and it wasn't merely an attempt at self-deception. In terms of jaw-dropping shock value, the show never got this brilliant ever again.