This page of the guide to GreedFall has a walkthrough for Saint and Wild side quest.
Where to start the quest?: Complete In the Footsteps of Saint Matheus side quest.
Take the tablets to camp - you will get +2 reputation with Theleme. Talk to Virgil/Eugenia. You now have two options - you can give the tablets to Eugenia or Virgil. This is the final moment to make a choice about what you want to do with the tablets - if you, for example, expelled Virgil during Theological Conflicts quest, then you can keep the tablets for yourself, find the man and complete the quest according to his expectations. Below you can find two options which depend on our choice
Give the tablets to sister Eugenia - You will receive +1 reputation point with Theleme. Brother Virgil will arrive, accompanied by a group of people. You have to kill him. You will be sent to the Mother Cardinal in San Matheus - tell her everything. During the dialogue with her, use charisma and intuition to try to convince her to reveal the message from the tablets. You can mention the Ordo Luminis attacks and have Siora in the team. Lastly, you can also mention the discoveries found in the tablets of Saint Matheus - you will get + 3 reputation points with Theleme.
Give Virgil the tablets- talk to brother Virgil (if you supported Eugenia, you will find him in Tir Dob). You are ordered to return to the cave of Saint Matheus and blow it up. Approach the highlighted points. Eugenia and her people will appear - kill everyone and then continue planting the explosives. Leave the cave - it will collapse, forever burying the secrets of the saint. Wait 24 hours and return to Virgil - he is with the Mother Cardinal. Complete the quest and gain + 3 reputation with Theleme.
Regardless of your choice, you will get 2,200 XP.