That's the weakest link in the whole chain.

The weakest link in the chain are your clients.

The weakest link in a chain is the strongest because it can break it.

A chain is only as strong as its weakest link

The weakest link in the chain is also the strongest. It can break the chain.

The bottom line is that a chain is only as strong as its weakest link. And I have to believe from past experience and knowledge that some of the links in Homeland Security are weak. Part of the story in "Lost Light" is about a weak link in the chain.