“在暗中”用英语怎么说？

我能肯定，他当时知道我在暗中调查他。I'm sure he knew I was checking up on him.很多人在暗中祈求和解。Many were secretly praying for a compromise.他们很清楚,我们在暗中设法对付他们.They were sure that we were conspiring against them....