Is the second verb in a french sentence always in the infinitive (if this is present tense)? For example: Les talons rétractent quand tu promene l'escalier.
Your sentence isn't correct, besides there is no infinitive in it.
Very often the infinitive follows another verb, in French.
Ex : J'aime nager (I like swimming)
Je dois parler (I must speak)
Except when the second verb is a past participle.
Ex : Après avoir dormi il est parti.
After having slept he left