1997 sci-fi/horror film starring Laurence Fishburne and Sam Neill (5,7)
I believe the answer is:
event horizon
(Other definitions for event horizon that I've seen before include "(In astronomy) boundary of a black hole - no Heinz voter (anag)" , "black hole terminates here" , "(In astronomy) notional boundary of a black hole - viz not hereon (anag)" , "Point of no return" .)