When saying k'riat sh'ma al hamitah, many (all?) people say the word emet at the end of the third paragraph. Also, I believe that the common practice when saying keriat sh'ma without the brachot (for example, saying it to oneself if the tzibur will not reach it on time) is to say it with the word emet at the end of the third paragraph.
But the word emet is really "borrowed" from the beginning of the first bracha after k'riat sh'ma. So why do we say the word when saying sh'ma without the brachot?