Danny is taking part in a ‘de-worming’ drugs trial at Leopard’s Den. But Caroline hates animals and, after a huge row with Danny, announces that she’s leaving. But she soon changes her tune when she meets Gerald, whose light aircraft crash lands into Leopard’s Den. When scientist Trevor hails the trial a success, Rosie takes him for a drink to celebrate.

Meanwhile, Evan and Olivia uncover Gerald’s secret cargo – his chimp Billy. Gerald confesses to Caroline that Billy is in South Africa illegally and persuades Caroline not to tell Danny, fearing that he’ll shop them to the authorities. Caroline agrees to keep his secret – providing she can escape with him to The Cape.

When Du Plessis finds a very sick cheetah, Danny thinks an exotic virus is to blame. But Trevor thinks that Billy could be the carrier and agrees to have the chimp quarantined. Danny is furious at Caroline for keeping the secret, which turns out to be one of many things Gerald has lied about…

In the middle of the night, someone lets the chimp escape. Gerald denies he’s responsible and he, Danny and Du Plessis set out to find her – and they have no choice but to kill Billy before the disease spreads any further.

Back at Leopard’s Den, Rosie wonders why Trevor is making a hasty exit. Could his drug testing be the cause of all the problems?