Last Night's TV: Homeland, Channel 4 (9pm)

No explosive ending, but the fuse is lit for Homeland's second series

We've all been there, I'm sure. You've plotted for years to get yourself to the heart of the American establishment, enduring captivity and torture. You've passed lie-detector tests, fooled an obsessive CIA agent and persuaded your family that you're back with them for good. The first half of your very complicated plot has gone perfectly and then, as success – and Paradise – is in sight, the trigger for your suicide vest fails. How do you get over an anti-climax like that? And, before you protest that you don't have anything at all in common with a suicide bomber, just remember that any devoted viewer of a serial thriller such as Homeland has also put in a lot of preparatory groundwork and is also hoping for a climactic blast.

We approach the final episode with mixture of manifest destiny and apprehension. What if something goes wrong with the plot? What if the whole thing ends up as a non-event?

The finale of the first season of Homeland finessed this problem neatly, with an episode characteristic of the series that preceded it. That is, it combined some infuriatingly implausible departures from the real world with a sharply pertinent proximity to it. And it infiltrated into the stock architecture of the spy thriller some genuinely moving psychological dilemmas.

The spine of the drama has been this: what if a professional paranoiac, someone paid to imagine the worst and prevent it from happening, began to look like an unprofessional paranoiac, deranged by suspicion? Claire Danes played that beautifully, her distress at being powerless to prevent an atrocity almost impossible to distinguish from a woman who simply hasn't been taking her lithium.

Damian Lewis got a double win out of the episode as well, revealed as someone prepared to go all the way, but also reprieved for series two. After frantically repairing the wiring on his bomb, he exited to have another go, but a last-minute call from his daughter made him change his mind. In the real world you can't help thinking he might have damaged his political prospects by appearing to have a full-blown nervous breakdown in front of the Vice-President and his cronies.

But in the more forgiving universe of television, the wobbling top of the narrative has been given a vigorous new spin. We know with certainty that Brody is ruthless now – he killed without a second thought to allay his controller's suspicions – but was that ruthlessness directed at protecting himself or prosecuting a new and deadlier plan?

Above all, for anyone sickened by the unthinking cheerleading for torture we got in 24, Homeland shines a harsher, more interrogative light on the corrupted forms that American patriotism can take. When Saul throws down a stack of DVDs on the neocon VP's desk, hinting that they contain incriminating footage of torture, the writers allude to a real instance of CIA skulduggery – the destruction in 2005 of videotapes of "enhanced interrogation" by a senior CIA man called Jose Rodriguez, an act he chillingly described as "just getting rid of some ugly visuals".

Brody's suicide video, seen at the beginning of the episode, talked of his Marine oath to protect the country from "enemies, foreign and domestic". His solution is, to put it mildly, extreme, but you don't have to be a suicide bomber to see that some of those enemies might have been voted into office.