Finally, her mother seemed to fall into a deep sleep.

She tried to fall into sleep once more, but could not.

I don't even want to go into the country and sleep.

All the students and their teacher go into deep sleep.

Just something to let you get over into a nice easy sleep, John.

She passed into a deep sleep once we got her in bed.

At which point she fell back into a deep sleep.

She took him through the dark back up to his room, and he fell into a deep sleep.

Perhaps it's because I can't get into a really deep sleep?

They all left the room, and I fell into a deep sleep.