Split Second is a 1992 British science fiction film starring Rutger Hauer, Kim Cattrall, and Neil Duncan. The film is directed by Tony Maylam and Ian Sharp.
Finally, after Stones girlfriend Michelle Cattrall is kidnapped, the detectives track the killer deep into the flooded and disused London Underground system and discover the truth the killer is not human. Its a horrific and possibly demonic form of life that is fast, savage, bloodthirsty and fixated upon killing Stone just as it previously killed his partner. In fact, as the movie progresses, each killing and appearance of the monster is an attempt to lure Stone closer and closer.During a tense battle in and around an abandoned underground train, Michelle is found suspended over the water as bait, but Stone is able to pull the monsters heart from its chest and kill it. However, as the policemen leave the scene with Michelle in a rescue dinghy, bubbles of air are seen breaking the surface of the water, suggesting that there may be more than one monster. ........
Source: Wikipedia