>To be doing something that will definitely have a negative outcome
>To be headed towards doom
>To be headed towards certain failure
The phrase which refers to no pass through from an alley was first used in 1583 by Richard Stanyhurst which was a literal reference to an alley. Its figurative form was used in the 1900’s.
>The exam was up a blind alley for me this time because I just did not have the time to study after working two jobs.
>She is headed up a blind alley being in a relationship with him.