The first challenge is called, High Wire. The teams have six hours to successfully build a mechanism that can traverse across a ten-metre-high wire. Dan and Kirsti’s Sloth Cable Car is the only build that makes it across. They secure their first win and an advantage going into the elimination round.
In the elimination round, the teams must create a mini fig scale, Secret City. The audience is privy to the secret; however, the mini figs are not. They have 10 hours to complete the build.
Having won the first challenge, Dan and Kirsti are given the advantage to allocate the six vacant city blocks to the teams.
As the teams build, Brickman reveals to Dan and Kirsti, that there is a second advantage to their win – there is another base plate under their benches. They can choose to reveal this to the other teams or not. They choose to keep the advantage to themselves, but, after seeing the other teams under distress, Dan and Kirsti choose to tell the teams.
Alex and Caleb set out to build an Evil Coffee Corporation. The secret is that there is an underground lair, where they are mixing toxic coffee in large cannisters. This is then piped to the local coffee shop, poisoning the citizens of LEGO city! Having come so close in the previous challenge, Alex and Caleb are keen to break from the pack.
Dan and Kirsti come up with the idea of an Alien Carnival. Dan builds a UFO which has crashed underneath the city. The aliens are then transported up where they join the street parade. Dan and Kirsti have so much fun with the build creating show stopping parade floats.
Lexi and Rachael work on a Hangry Statue that has come alive. They create a cave below the city, where the statue collects signs from around the city and eats them. Brickman tells Lexi early on that this must be the best character she has ever built. Feeling the pressure of the impending elimination, Lexi accepts Brickman’s challenge and is confident she can do it.
Henry and Joss, settle on the idea of creating Plaque Busters. The secret is that the dentist’s office is actually a secret hideout for the dentists. They moonlight as the Plaque Busters who are fighting off a giant candy monster that lives below the city.
Gene and Nick, create a Thieving Magpie, a modular build full of mini fig vignettes. The incompetent police department are trying to crack the case of stolen items in LEGO city. What they don’t realise is that there is a giant thieving magpie living on top of an apartment that is hoarding all the stolen items in the city.
Paul and Trent are excited to build their transformer Bus and Video Cassette action scene. Brickman reminds the boys that they are not building an action scene but a secret within the city. They then come up with a new idea Gaming Grannies. There is a secret tunnel underneath the local library where the senior citizens create games that the children become addicted to. As Paul and Trent get the build underway, they soon realise that their library and the below gaming lair don’t line up. They settle on the underground lair becoming a cutaway; however, it now exposes the secret of their build.
Time’s up and all teams have created spectacular secret city blocks. Alex and Caleb, Dan and Kirsti are called forward as the top two teams.Caleb and Alex win the titanium brick of triumph for their superb storytelling.
Trent and Paul and Lexi and Rachel are at risk of going home. In the end it comes down to the technical and the girls statue wok saves them.