S7, Ep 8: Paper War. When Higgins unwittingly causes Magnum to wipe an expensive computer game loaned from T.C., and Thomas accidentally erases a chunk of Higgins' memoirs stored on the computer, a feud breaks out between the pair. Magnum is trying to break a major, crooked gambling ring that is operating on the islands, but it is none too easy while in the middle of the falling out with Higgins, which starts out with each trying to out-do the other with "eye for an eye" practical jokes, and quickly develops into a particularly bitter battle of wills - one in which Thomas accuses Higgins of being Robin Masters!.
Starring Tom Selleck, John Hillerman, Roger E Mosley, Larry Manetti, James Shigeta, Richard Narita, Gillian Dobb, Lance LeGault, Kimo Kahaona, Clay Wai, Robert L Silva and Harold JK Iseke. For me this is easily one of the worst Magnum episodes ever made. There is a crime here (other than the script), but that is overlooked by petty vindictive pranks that really do not reflect well on Magnum's character. And it also starts the new obsession with Thomas on his theory that Higgins is really Robin Masters. If that's the case, wouldn't he be a bit more respectful of his employer?