Connor is furious with Callum for hooking up with a girl he was chatting up at the bowling alley. When Maureen Evans asks them to do a mission together, the two begin arguing and come to blows, with Callum accidentally kicking Maureen in the fracas. Maureen orders them to set aside their differences and do the mission or receive a severe punishment. The two reluctantly agree.
McEwen confronts jewelry businessman Steve Nolan and threatens to expose his tax fraud unless he co-operates with a CHERUB mission to plant bugs in the offices of several South American diplomats who are selling illegally mined diamonds. Nolan, who has had previous tax issues and is unwilling to spend time in prison, agrees to help.
McEwen and Callum disguise themselves as engineers and infiltrate the embassy, hiding in a meeting room, while Connor, posing as Nolan's nephew, tags along to a meeting between Nolan and one of the corrupt diplomat, Ramiro. As Nolan and Ramiro walk to Ramiro's office, Connor turns back, ostensibly to chase after a dropped cricket ball, but instead switches with Callum, equipped with listening devices. While Nolan examines the diamonds, marking them with a chemical marker, Callum plants the bugs. The meeting goes without a hitch and Callum and Nolan depart without suspicion.
- The information collected by the bugs lead to the arrest of Ramiro, 17 associates and 5 diamond dealers. Ramiro escapes prosecution due to his diplomatic status and close links to his country's president, but most of the other conspirators receive jail sentences.
- Steve Nolan's jewelry business goes bankrupt in early 2009 and he begins selling his own range of jewellery (made with artificial diamonds) on a shopping channel.
- The girl Callum and Connor were hitting on discovers that they are twins and, assuming they were playing a joke on her, threatens to thump them. The two reconcile a few weeks later.