'for fear the agents of other firms should be able to...'为什么

'for fear the agents of other firms should be able to...'为什么'for fear'后能加谓语?
Sometimes the secrecy goes to such an extent that the whole nature of the research cannot be mentioned.Many firms,for instance,have great difficulty in obtaining technical or scientific books from libraries because they are unwilling to have names entered as having taken out such and such a book,for fear the agents of other firms should be able to trace the kind of research they are likely to be undertaking.