If Topaz Had An All[-Star Cast...
Alfred Hitchcock made "Topaz" from a best-selling novel by a writer named Leon Uris, who had also written the epic novel "Exodus," made by Otto Preminger into an all-star epic.
Directors like Preminger and Stanley Kramer oftened used all-star casts to "sell" dramatic epics, particularly if the subject matter was grim (as in Kramer's "Judgment at Nuremberg" with Spencer Tracy, Burt Lancaster, Marlene Dietrich, Monty Clift,etc.)
Hitchcock wasn't much into all-star casts, and with "Topaz" he couldn't find even ONE star to be in it. Paul Newman and Julie Andrews had been the big stars in his last movie, "Torn Curtain." He didn't like them, they didn't much like him, no stars showed up for "Topaz."
But if Hitchcock had REALLY wanted "Topaz" to properly "play" as a dramatic historical epic -- what with the stories jump from Copenhagen to Washington DC to New York to Cuba to Paris and all sorts of characters interacting -- then it should have had a cast of 1969 stars, like this:
Andre (heroic French spy): Yves Montand
Nicole (his beautiful blonde wife): Catherine Deneuve
DuBois (heroic black French spy): Sidney Poitier
Nordstrom (American CIA boss): William Holden
Rico Parra (Castro lieutenant): Burt Lancaster
..and "Elizabeth Taylor as Juanita De Cordoba" (Andre's beautiful Cuban lover.)
Then, "Topaz" wouldn't have had to be too exciting at all (and it wasn't) to be a big hit.
But as I say, Hitchcock didn't work like that. So it didn't get a cast like that.