गूफ़

When the agents are preparing to do the first survey of the house they are wearing CD (Civil Defense) arm bands on their right arms. The next scene shows them approaching the house and the arm bands are now on their left arms.

The description of a one-way mirror as an "X-ray" mirror at the beginning is nonsense. A one-way mirror is in fact merely a partially-silvered mirror. It becomes "one-way" by virtue of different lighting on either side - one side dimly lit, the other brightly lit. From the side that's brightly lit, it appears to be a normal mirror because the reflection washes out any light coming through from the dim side. But from within the dim side, everything on the bright side is readily visible because the light coming through predominates over the reflection seen from the dim side.

There is no such thing as an 'x-ray mirror'. What they are using is a one-way mirror.

Early in the film when the German agent is run over in the street in New York, he is taken away by ambulance. The medic tending him tells the driver not to bother driving aggressively because the man is gone. BUT for the duration of these scenes this dead man eyes can be seen to be fluttering opening and closing as well moving about! Pretty neat trick for the dead.