为什么 npm 安装说我有未满足的依赖？

I have a node package. When I run npm install from the package root, it installs a bunch of things, but then prints several error messages that look like this:

npm WARN unmet dependency /Users/seanmackesey/google_drive/code/explore/generator/node_modules/findup-sync/node_modules/glob requires graceful-fs@'~1.2.0' but will load

I must be confused about what exactly npm install does. If it detects a dependency, shouldn't it install it? Under what conditions does it give me error messages like this, and how can I resolve the dependencies?