Not many hard details are known about Jack Donovan's life or career, except that he was a close friend of Immortal Connor MacLeod. He was residing in Marrakesh, North Africa near MacLeod and his adopted son, John. He served as a confidante for Connor, frequently advising him on various issues in his life.
In the year 1994, Donovan became involved in the events surrounding the return of the Immortal Kane and his henchmen, and took care of John when MacLeod journeyed back to New York City which had been the site of The Gathering in 1985. Donovan, however, was duped into placing John on a flight back to America by Kane, resulting in John's life becoming endangered during the final battle between the two Immortals.
An unofficial fan-theory exists which speculates that possibly Jack Donovan is a member of the Watcher organization, and is conducting covert observations upon Connor MacLeod during the events of the film.
The movie itself was shot well after the introduction of the Watchers on Highlander: The Series; however, there is no direct evidence in the film linking the character with the organization. Additionally, Connor's Watchers during the time period of the original movie and TV series were established as being Martin Holecek and Dana Brook.