Tensions simmer at school when new boy Nick stands against Marcus for school president. Tim tries to help Marcus but, given previous form, is more likely to hinder the campaign. Operation Sabotage is in full swing back at MI5 as Tim offers Caitlin and her presumed-dead but now actually very much alive fiancé Portis some rather dubious relationship advice. New counsellor Owen makes an impression too, taking a particular shine to Judith.

Tim is asking for trouble when he falls for a woman in the Witness Protection Programme, and Marcus learns how to ride a bike.

Maintaining a secret identity is a mighty ask, and there's every chance that Tim's cover is going to be blown when he's forced to take Marcus to work with him. Also, there's extra cringe in this week's therapy session when Owen leads Philip and Judith in an elaborate role-play exercise.

The Examiner is on star-spotting duties and casts Tim and Caitlin in a recruitment video. It seems like a perfectly good idea until the pair let their disguised identities get the better of them.

After Judith receives a blow to the head she wakes up believing that she's still married to Tim. Poor Philip is understandably devastated, but on hand to pick up the pieces is Chris, who believes the best course of action is to reintroduce him to the dating scene right away.

Marcus's hopes of organising the Summer Ball are dashed when the dreaded Mrs Godfrey usurps Philip as the school headteacher. Meanwhile, struggling to find a date, Tim tries to improve his luck with the ladies. Maybe he should take a leaf out of Bond's book.

After bumping into his MI5 body double, who happens to be a genius, Tim agrees to compete for custody of Marcus. Moritz, meanwhile, is asking for trouble when, crossing all sorts of lines, he tries to woo a hostage's anxious girlfriend.

While Chris tells one porky too many in a bid to turn Marcus into a celebrated author, Portis busily prepares for Caitlin's birthday, but fails to factor in a major obstacle in the form of saboteur Tim.

Tim is given extra incentive to rekindle his romance with Caitlin after finding himself on an assassin's hit list. Marcus, meanwhile, has been biding his time and is in prime position to humiliate rival Nick at Justine's dinner party.

In an hour long Christmas special, the magic of Christmas has long been lost on Marcus and, when his party plans force the other kids to go on strike, he must make alternative arrangements. Meanwhile, 'tis not the season to be jolly if you're Portis. The agent's thoughts turn to revenge after he finds out about Tim and Caitlin having feelings for one another.