The next adventure so far released is C, called Ship of Doom. It can be run on the 48K Spectrum and 16K ZX-81.
Your ship is captured by aliens who are searching for humanoids to replace their brains with microchips. The object of the game is to escape from the alien craft by breaking the gravitational field. To do so you must find the control room of the alien ship.
The help command is a little more useful in this game and it is easier to get further when playing the game.