As we reach the halfway point of Series 9, this week’s episode sees the new Spooks team starting to work together as a unit.

After a shaky start, new girl Beth (Sophia Myles) seems to be gaining the trust of her colleagues, but in this mission her main task is to gain the trust of an asset, Kai, who works at the Chinese Embassy. This becomes critical when the team are faced with a threat from Chinese spies.

A team of known Chinese agents arrive at Dover, apparently looking for a scientist who has made a breakthrough in the desalinisation process. MI5 have to take chances with their asset in order to uncover the true extent of the threat, but when Beth reveals her true identity Kai walks away, determined not to betray his homeland. This puts the usually office-bound Ruth in danger as she goes undercover at the QMK research facility when the plan is put into action.

In some ways, this is a slow burner of an episode. After the high-octane start, maybe the writers wanted to give viewers a slightly overdue chance to acquaint themselves with the various newbies (Max Brown’s Dimitri in particular is still desperately underdeveloped). This seems to be a successful approach as Beth settles down as a full member of the team.

Meanwhile, Lucas’ (Richard Armitage) former life still looms large and leads him to consider a risky ploy to get the shady Vaughn off his back. There are signs in this episode that at least one of his colleagues is starting to get suspicious, no matter how carefully he tries to cover his tracks.

The secret of Spooks’ success over the past decade has been the way the storylines have incorporated economic and political issues, sometimes before they have been in the news. Here they touch upon the issue of water shortage with some very grim warnings about the near future.

Despite still feeling the absence of Ros, arguably one of the show’s best ever characters, this series shows that the writing has not lost its edge, which is quite a feat after so many episodes (76 and counting). It looks as if Sir Harry’s resignation letter may be gathering dust in the Home Secretary’s desk for a while yet.

Airs at 9pm on 11th October 2010 on BBC One.