An inverted sentence is a sentence in a normally
subject-first language in which the predicate (verb) comes before the subject (noun).
Down the street lived the man and his wife without anyone suspecting that they were really spies for a foreign power.
Because there is
no object following the verb, the noun phrase after the verb "lived" can be decoded as subject without any problem.
In English, such an inversion often introduces
do-support.