Water leaking in through door on main floor down to basement.
Look at the way it was caulked, a blob of rounded caulkiing is forming a funnel not a seal.
It should have been 100% silicone that was rounded with a finger not just what looks like a tube of it.
Also I'd bet there not one of these under it. http://www.jamsill.com/
With a jam sill there's no way for water to get in.