You play Kim Kimberley, secret agent extraordinary.
Your mission: to safeguard the interstar transport, Snowball 9, as a last resort following catastrophic accident or sabotage.
Thus when your modified freezer-coffin wakes you with the Snowball still in transit, you know that something must be very wrong. You're weakened and disorientated from lengthy hibernation, but the fate of two million passengers is in your hands!
When the game was released, it was touted as having more than 7,000 locations. In reality, the game size is more akin to Level 9's comtemporary releases (~200 locations), with the remaining locations being a colour-code maze of otherwise idential rooms.
If I remember correctly, some versions of this game had a prerelease piece of code left in; if you typed "daytona" the Waldroid appeared and killed you.
This is probably inspired by the Acorn BBC wordprocessor View easter egg, where if you typed DAYTONA it responded "Mark Colton", the author of View, who also was a racing driver (so it makes kind of sense). However, I haven't seen this confirmed in Snowball. Neither the BBC and Spectrum versions seem to have it.
I am going back over forty years, but I seem to remember reading it in a review of the game shortly after its release in 1983 I believe; I really cannot recall which PC magazine it was however. It may even have been in an exchange with one of the Austin brothers but it sticks in my mind as so many useless things do.