Diagnosing Source of Water Damage on Basement Wall

before calling a contractor, i would do as others have done on here; go to the roof and check the capstone joints for voids, the roof membrane where it meets the parapit wall (inspecting the roof membrane at the parapit wall is a monthly detail for professional site managers, i think, i think it is done monthly; i inspect my roof in the spring and fall and just did mine), and if this is at the edge where the membrane flows off into a gutter, that the gutter is not clogged and sending water between the facia and membrane.

the reason i suggest you look first is, a roofer might have a better idea about what is going on upstairs but less downstairs and vice versa. i am a contractor and spent a lot of time chasing leaks and in large buildings they can appear in one place and the entry point may be someplace else. some are obvious and some less and not all contractors (and i am including me in this; i am not putting myself forth here) are going to have less luck than others locating this and then dealing with it.

roofers are a dime a dozen. i would wait and see what others say about someone who can locate something that might be coming in through the wall. experience will tell these folks how far water will move through concrete and masonry from the source; it might be right there, it might not be.