It’s nightfall on the island of Zanzibar and somewhere out in the Indian Ocean Kate is in need of rescue.

The scientists’ challenge is to equip Kate with everything she’ll need when she’s lost at sea: They have three days until Kate will be in the water, in the dark and putting their creations to the test…

Mike has the task of making a distress flare that will pinpoint her position out in the dark. Meanwhile Ellen and Kathy have to make a life jacket – it’s got to stay together and keep Kate afloat until the team can get to her. Jonathan’s job is to design a beacon – something that will help the team spot her from the rescue boat.

The trunk is very bare and this week the pressure is on. The team have no choice but to rely on the natural resources of the island. Mike goes hunting for an explosive ingredient in the local bat cave and Ellen and Kathy get sticky at the island’s rubber plantation. Jonathan, meanwhile, tries to make light from sea water.