A friend of mine described this situation to me recently:
The scene is a hotel lobby in the middle of the night. Three people, two men and a woman, enter. The woman appears to be drunk and unconscious, and is being supported by one of the men. The other man smells of alcohol, but is otherwise sober. They try to get a room. The receptionist, aware that the hotel is situated in the vicinity of a red-light district, is suspicious and lies that there's no room available. The trio say okay, they'll try another hotel, and leave. The receptionist then calls the police.
Can the police act? On the one hand, the circumstances can be interpreted as a rape has happened or is about to happen, e.g. a date rape drug that knocks the woman out has been administered; on the other hand the receptionist can't be sure of that and the three could e.g. be blood relatives or even good Samaritans.
If this does meet the threshold for "reasonable suspicion", does it further meet the threshold for "probable cause"? If this does not meet the threshold for "reasonable suspicion", is it worth calling the police in this situation?
If it matters, the country is Singapore.