piece of the puzzle
piece of the jigsaw

Another puzzle piece in place, and I still couldn't put the whole thing together.

One piece of the puzzle she would keep to herself.

And now he had another major piece of the puzzle.

Now her death had become one more piece of the puzzle.

"We have only one more piece of the puzzle to find."

"But to get every piece of the puzzle they need more time."

"That is the piece of the puzzle I have yet to figure out."

And at least one piece of the puzzle now fit.

At best, her research points to another interesting piece of the puzzle.

The moment he did, another piece of the puzzle fell into place.