State of Decay: Year-One

This is a quest in the standard campaign which comes up as you're playing along. It'll show up as "A Discreet Request" where you need to talk to Quentin which you help earlier on.

He wants you to find out information about Becca since he needs to be sure about the relationship. Head over to the Courthouse looking for the Sheriff, he'll be somewhere else but you need to do that first.

The Sheriff is off looking for a Feral zombie, you'll just have to head over and find him, then take out the Feral. After disposing of that the Sheriff will give you the details and you need to make a decision of how to present it to Quentin.

"Edit" Guess I wasn't clear, you must say yes initially and do up to the Sheriff part, then say No.
If you want this right away just say "NO" it's best to leave things in the past and the achievement will unlock instantly. You can also play it out with the tell the truth option, but just saying "NO" is much simpler.

Guide courtesy of Gamerheadquarters

This achievement was the only one that I missed whilst playing a blind-playthrough.

I had to play the game multiple times to get this single achievement to unlock so sharing my brief guide and tips here.

This achievement unlocks when completing the questline from the survivors at 'The Grange'. They are located on the road heading North from the town in the SW corner of the map: .

Their missions start to pop up after you relocate your home base from the church. After doing a few missions for this group, including where you defend them as the build a tower, you will get a mission from Quentin called 'A Discreet Request'.

1. Accept the 'A Discreet Request' mission. Complete it. This will involve you having to go find the Sherrif and defeating a Feral zombie. The Sherrif then tells you about the girl's past.

2. Return back to Quentin. You will be given two options. Tell Quentin the truth. Do not pick the option corresponding to 'No'.

3. Immediately follow Quentin into the store their store and there will be some dialogue which results in him storming off and disappearing from the enclave.

4. You now need to wait a long time for the next mission to appear. It took something like 3 in-game days (6+ real life hours at least). I was after the 'Insubordination' mission from the Army and the point in the story where the enclave in the court had fallen apart (Judge and Sherrif died) -- it took at least an hour after that, maybe more.

5. The final mission is called something like 'Quentin Barnes?'. Go pick him up and take him back to the Grange to conclude this quest.

I don't think any of the missions are missable or have special criteria to appear, so don't stress about it. Sometimes it takes a long time for missions to appear in this game so just keep knocking out side-quests, returning home and going into your base (in case there are any cut-scenes pending) and accept the day-night cycles in this game take a while.

The popular recommendation is to do the opposite of what I state in #2 above. I have seen videos of the achievment unlocking at this point, ending the quest line. However, this is what I did on my first playthrough and the achievement did not unlock. I did a second playthrough up to this point and did the same thing and it did not unlock. I then deleted my save and reloaded from cloud several times, and no achievement.

I then did a third playthrough to get this to unlock. So, save yourself some hassle and just tell Quentin the truth about his girlfriend. Sure, it delays unlocking the achievement but the extra quest is exceptionally simple and it was the only way I could get it to pop.

I recommend backing up a local save before you complete the quest line to save yourself hours if you have to replay the game as I did.