alle or alla

Question

Après ________ voir son oncle, Marc alla se promener.  'alla' is passe simple so obvs from a book. why is the perfect infinitive used int the etre alle clause after apres.should that not also be alla?

Accepted Answer

You use the perfect infinitive after après if you want to express "after having done something".
Après avoir vu son oncle, Marc alla se promener. -- After having seen his uncle, Marc went for a walk.

Answer

Yes I understand that, but the rest of the sentence is in passe simple, so presumably from a book. Therefore in the context of a book, the use of passe simple does not apply to apres que. How about the subjunctive? Is that used in books? If so, then when exactly does the passe simple apply? only when you would use the passe compose?

Answer

Avoir vu