Sewer Rat / Raiders

In this text adventure, you play the friend of a professor who has gone missing on some kind of archaeological survey. Your task is to find the professor, or at least to find out of his fate. On your adventure, you will ride the taxi a lot (and must find a way to pay the driver), travel by airplane and visit a remote, mysterious island. The command interpreter is of a rather simple verb-noun mould, with some peculiarities such as SAYing your wishes to the taxi driver.