Trini has been standing in the freezing cold, threatening to become almost as sick as Marc. Lisa gives a demonstration on feeling hot and cold. But the biggest surprise comes when Lisa brings in Vicky Johnson, an engineer who designs life-support systems for astronauts. On location: Lisa witnesses an infrared camera. Trini learns about protecting the human body from the cold while climbing a mountain.ANIMATION: Fahrenheit vs. Celsius.THE BLOODHOUND GANG: ""The Case of the Secret Message, Part One."" Vikki recovers a lady's purse, which contains only a message written in salt-water solution. (Concludes in next episode.)