Dirk Gently's Holistic Detective Agency (Douglas Adams 1952-2001) - Pocket Books - 1988

Dirk Gently (not his real name) cannot always pay his receptionist on time but he does save the future of mankind on a regular basis.  In this episode, he gets some assistance from an ancient professor of chronology who performs magic tricks and has a horse in the upstairs bathroom.  And, caught in the middle is young Richard MacDuff, a software designer who is dating the sister of his boss, who has some kind of alien portal in the trunk of his Porsche, and is trying to erase a phone message he sent to her. [Why don't you try to diagram that sentence?]  You may need to read this one twice to determine what the heck is happening. [JAM 3/3/2010]