I haven't seen I Saw What You Did, alas, but the descriptions are making me think of a very weird film from the same period with Peter Sellers and Angela Lansbury, The Secret World of Henry Orient. Or, for that matter, The Trouble with Angels with the immortal Roz Russell.

For some reason, around 1963-65 there seems to have been this mini-trend to construct films populated with well-known, highly talented, mature name actors whose stories revolved around the antics of two teenaged girls who needed severe disciplining from their Dads (to use the argot of the period).

Don't forget, Joan always laced her vodka with Pepsi in the Sixties.

H.