Plus is a word in French which insists on changing its personality. It is also a word which set our teacher's teeth on edge, because I couldn't help but laugh everytime she tried to explain why it did what it did.
Il y a plus de femmes dans la rue. (There are more women on the street.) Here you say the s with force. However if you say, c'est plus facile, (it is easier) you don't hear the s at all. It disappears into some cave somewhere, though Irene tried to explain the reason.
If the sentence is c'est plus haute, (it is higher) the s sounds like a z and it connects with haute, because the h is silent. Therefore haute acts like a word starting with a vowel. So you hear plu zaute.
If you add to a sentence ...en plus. Again you get a very strong s sound.
Now remember at the beginning, if you say Il y a plus de femmes dans la rue, plus has a very strong s sound. However, if you say Il n'y a plus de femmes..., then the plus loses the sound because it's a negative (n'y). Go figure. But it keeps you guessing. And as boring as it may be, you don't dare fall asleep.