THE world's largest off-limits preserve, so far as journalists are concerned, is a Red China so tightly sealed that it makes Soviet Russia seem an open book. We can only do the best we can, from the outside peeping in, and are always unhappy that we can't do more, for Red China remains one of the world's big stories and its most underreported one.

Once before, on a previous TIME cover story, we described how we go about collecting material from our Hong Kong listening post (whose collection of books and newspapers is famous enough to draw visiting scholars), from Communist radios monitored and Communist newspapers read, from working closely with government agencies, both public and clandestine, that deal with the mainland, from resident Sinologists in the universities here and in Britain. Some of our sources are insistent that they not be identified. China watching has become a major industry. We are grateful for the help, and find most government people and scholars very ready to share information and analysis. In this way, we are able to run a wide check on the conclusions we reach.

But life in China is more than crop reports, trade statistics and propaganda analysis. We seek also the vivid eyewitness detail. Here are some of the people interviewed for this week's story:

sbA large number of refugees, including a chemical engineer from Tientsin, one of the few refugees interviewed in Hong Kong who had much to relate beyond the food conditions in his own village.

sbThe mainland specialists of the so-called Sixth Section of the Kuomintang Party in Formosa.

sbA Belgian turncoat prisoner of war in Korea, who has just left China "politically disillusioned."

sbBritish industrialists lately returned from Red China.

sbA handful of traders who pass in and out regularly.

sbAn important Chinese defector now in a European country.

One of the key documents was a Red Chinese officer's secret report smuggled out of China, presumably via Tibet, and released to TIME by the State Department. Sybil Wong, who with Shirley Monck did the bulk of the cover researching in New York, spent several days translating the secret report for Writer Robert McLaughlin.

The job for McLaughlin, whose 25th cover story this is, became one of assembling a mosaic out of varied, and often conflicting, reports. Two of our foreign sources--who did not know each other--happened to be riding on the same train in China. One described it as filthy, with bugs and bad water. The other thought it clean and the service fine.

No wonder our editors, writers and correspondents are never content until they have talked to every traveler to China or every important refugee they can find.

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