Let’s begin with a simple statement. femina homines spectat. ‘The woman is watching the people’. Now, let’s rework this with a Passive Verb. homines a femina spectantur. ‘The people are being watched by the woman’. Each of these sentences is a Statement.
Now, let’s make the first sentence into an Indirect Statement. In English, we might write something like ‘The woman knows THAT she is watching the people’. But in Latin the grammar is something more like ‘The woman knows (scit) herself (se) to-be-watching the people.’ Did you notice the absence of 'THAT' and the change to the Infinitive Verb ‘to-be-watching’? It will be easier once we see it written in Latin; femina scit se homines spectare.
Now, let’s make the second sentence into an Indirect Statement. In English, we might write something like ‘The people know THAT they are being watched by the woman.’ In Latin, however, the grammar is more like ‘The people know (sciunt) themselves (se) to-be-being-watched by the woman. Did you notice that this time the change was to a Passive Infinitive, ‘to-be-being-watched)? Now, let’s see the whole sentence in Latin; homines sciunt se a femina spectari.
Look! This room is occupied. Two people are secretly (clam) conversing among themselves. The people do not know that they are being watched.