It’s hard to imagine a better end to the sixth series of Spooks than the hour we were treated to last night. The tension that has existed between MI5 and the CIA throughout the series built to a crushing climax as Bob Hogan was revealed to be a renegade, Section D’s two top operatives were captured and we finally learned the truth about Zaf.

So, all loose ends tied up neatly then? Well, not quite. There is just one small question remaining.

After the Americans go ahead with their air strikes against Iranian targets, and a school full of children is hit in the process, al-Qaeda announce they will launch an attack on a British school in retribution. Section D learn from the Venezuelan secret service that the visiting Venezuelan president is being targeted by CIA hit-man Annibal Rodriguez, and the Venezuelans are interested in a trade – if MI5 can stop the assassination, they will share their intelligence on the school attack.

Zaf’s tortured corpse is found and Bob Hogan identifies the group responsible. They call themselves the Red-backs and their speciality is torturing spies to extract intelligence. They kidnap Jo, and when Adam asks Hogan to negotiate her safe return he’s horrified to discover Hogan is one of them and Adam ends up being captured too.

Ben, the journalist who seems to have been able to turn himself into a spy overnight with no apparent previous aptitude or training, apprehends Rodriguez before he can kill the Venezuelan president, which angers the CIA who are responsible for arranging the assassination.

Harry finds himself in a cleft stick. The CIA get to Hogan before Section D and although Hogan is prepared to release Jo and Adam, the CIA won’t let him talk to MI5 unless they get Rodriguez back. But if Harry settles for this, the Venezuelans won’t give him Harry the information he needs to stop the attack on the school.

Harry worms his way out of this situation by telling the CIA Rodriguez is dead, but he does a deal for the intelligence about the al-Qaeda attack.

Meanwhile Jo tells Adam about her father and his bird-watching. How easy it was to let an injured bird die just by holding it gently in your hand. The bird is a metaphor for Jo. She can’t face being tortured – or worse – and asks Adam to kill her himself. At first he refuses, telling her there’s still a chance they will be rescued, but she pleads with him and as the special ops rescue team rush to engage with the Red-backs, Adam takes Jo gently in his arms until she collapses. But is she dead?

Another cliff-hanger ending for Spooks, which really hit the heights throughout this series. A seventh series has already been commissioned and will begin filming in Spring, but even so it will be a long wait to find out whether or not Jo survived. I hope they revisit this idea of a series-long story arc. It worked well this time out and allowed the dramatic tension to build over a much longer period with a small peak in each programme accompanied by a devilish twist. I had a slight worry that they were killing off too many highly trained operatives but if they can pick up a few more journalists like Ben and train them up in no time flat, that shouldn’t be too much of a problem.