The Empire of Sirius, formerly the enemy of Canopus, has now for some time been its uneasy and mistrustful ally. Though highly advanced technologically, and despite being sophisticated social engineers, the Sirians are suffering some upheaval because of the many members of their population who feel that their life lacks a worthy purpose. Ambien II, a member of the Five who govern the Empire, is befriended by Klorathy, an agent of Canopus, in the course of their mutual dealings upon and around the planet Rohanda. Ambien II's education in the means and motives of Canopus, and her eventual realisation that, doubtless unique in the history of galactic diplomacy, Canopus means what it says and does what it promises, is the major subject of The Sirian Experiments. Doris Lessing has written, "I could like Ambien II better than I do;" which is a pity, for Ambien II, along with Rachel Sherban in Shikasta and the incensed innocent Incent in The Sentimental Agents in the Volyen Empire, is one of the most appealing characters in the quintet. Her growth from efficient, obedient social scientist (who deplores the changing of our planet's name from Rohanda (Fertile) to Shikasta (Wounded) as showing "a mixture of poeticism and pedantry typical of Canopus") into willing pupil, sometime rescuer, and eventually into that amazing paradox, the clear-headed visionary, is a triumph of characterisation. Her report - careful, thorough, just and drily humorous - betters Shikasta in its fusion of the personal with the cosmic, and contains one of the most spectacular set-pieces in the whole series, as well as some of its most poignant personal encounters. The ending is quietly ironic, without the sense of definite progress which was present at the end of the previous two books - the major breakthrough here takes place inside Ambien II herself, though further, exterior victories may just possibly be on the way. This book (not to mention the quintet as a whole) is the kind of thing science fiction was meant to be all about.