I kind of know 'Equus' - it was one of the old productions of the American National Theatre of the Deaf / DeafWest, and I saw some video clips of it.
It was amazing to see the horses recreated through props and sign language.
The lead actress, Phyllis Frelich (also deaf) went on to lead 'Children of a Lesser God' when it opened on Broadway.
In the Hollywood film version, her part was acted by Marlee Matlin, who now stars in 'FB Eye', a series on a TV near you about a deaf FBI employee.
When 'Children of a Lesser God' came to UK theatres many years ago, the lead part was acted by a British deaf actress, cos it had to be in BSL (British Sign Language) not ASL (American Sign Language, a very different language to BSL).
That British actress is now my partner. Guess I'm now only 4 degrees seperated from Harry Potter