Mahoney was always grateful for what “Frasier” had done for him and took care to say so on numerous occasions. His success on that show meant that, thereafter, he could focus on Chicago theater, his great love, and on the Steppenwolf Theatre in particular. By not having to worry about money, he was able to work on what he wanted — like acting for scale in “Long Day’s Journey Into Night” at Chicago’s tiny Irish Repertory Theatre. But over the years, he lavished most of his time and attention on his beloved Steppenwolf, appearing in more than 30 productions in total at the theater, including Conor McPherson's "The Seafarer" in 2008, perhaps Mahoney's most devastating performance, if only for the way it emphasized his inherent frailty.