As Arthur:
You’re all hiding behind the computer bank. There must be a way to escape the two firing officers on the platform. Right click and switch to Marvin.
As Marvin:
You’re bored. Try to talk to the police craft, but it doesn’t understand you. Talk to the rock to the right of the spaceship and express your depression. That’s the only way the rock will be moved. Behind the rock is a panel. Plug into the panel and you can talk to the spaceship. While the conversation is going, the officers have died.
As Arthur:
Now that the firing has stopped, use the corridor and go through. You all agree to take the aircar for a ride but then there should be some sort of power. Look at the pumps on the right side. Tease the pumps and when you leave them you get an indication that all levels should be the same. When the levels are not high enough, you’ll be notified as well.
Set the pumps to the second (50) or third (80) level. All three levels should be equal. Use the aircar to get in and you’ll all be reunited with Marvin next to the police craft. Look, talk or interact with Marvin the learn about his mood. He’s very depressed. Even the air ship comitted suicide.
At the Heart Of Gold you start to read in the Hitchhikers Guide to the Galaxy. You’ll learn more about the universe. Then Eddie tells you the course is set the Restaurant at the end of the Universe.
Game source: A copy of the game was found here on the internet.