The Monster Inside - 100% Achievements Guide

• ⭐ Difficulty: 1/10
• 🕓 Estimated time: 20 minutes
• ❌ Missable achievements: None

Let's get one thing straight from the start – this is one of the easiest 100% completions you will ever earn on Steam. There are 7 achievements in total, every single one of them is story-related, and not a single one can be missed. You do not need to make any specific dialogue choices, you do not need to replay any chapter, and there are no hidden collectibles to hunt down. All you need to do is play the game from start to finish. That's it.
Still, if you want to know exactly what to expect chapter by chapter – read on.

General Tips Before You Start

The Monster Inside is a visual novel with light point-and-click investigation segments. A couple of chapters will ask you to click on specific objects in a scene before the story can continue. These are not difficult or timed – the game will not move forward until you interact with them, so you cannot accidentally skip past anything important.

The game does not have a text speed setting and does not support auto-advance. You can click through dialogue manually at your own pace, or simply let the story breathe and read everything properly. The full experience runs around 15 to 20 minutes depending on your reading speed. Rushing it by clicking fast is possible and will still unlock all achievements – but honestly, you're here for 20 minutes. You might as well enjoy it.

All 7 achievements unlock automatically as you complete each chapter. There is no secret ending, no alternate path, no New Game Plus. Just play it through once.

Chapter-by-Chapter Breakdown

Chapter 1: The Banker
Achievement: Complete Chapter 1
The game opens with your detective, Jack, taking on a missing persons case involving a mysterious woman named Lilly. Chapter 1 sets the tone – dark, moody, and written in classic noir style. Read through the dialogue and let the story introduce itself. No interaction required beyond clicking through the text. The achievement unlocks at the end of the chapter automatically.

Chapter 2: The Park
Achievement: Complete Chapter 2
Jack heads to the park to investigate the scene of Mrs. Farnsworth's death. This is your first chapter with an active investigation segment. You will need to click on two items in the environment: the muddy footprints and the burn marks on a nearby tree. Click both to trigger Jack's observations and continue the story. The chapter concludes with Jack heading back to his apartment and the achievement unlocks.

Chapter 3: The Police Chief
Achievement: Complete Chapter 3
Lilly pays Jack a visit at his office with an update – the Police Chief's wife has been found dead at the docks. This chapter is dialogue-only, no investigation required. Just read through the conversation and the achievement will unlock at the end.

Chapter 4: The Docks
Achievement: Complete Chapter 4
Jack arrives at the docks to investigate the second murder. Another investigation segment here – click on the cigarettes and the small piece of purple fabric near the lamp post. Both are relevant to the case and Jack will comment on each one. The chapter closes on a quieter, more introspective note before the achievement pops.

Chapter 5: The Mayor
Achievement: Complete Chapter 5
Things start getting stranger here. Jack's mental state begins to fray as the case takes on an increasingly unsettling edge. This chapter leans more into dialogue and internal monologue. Stay with it – the story is building toward its payoff. No interaction required beyond reading. Achievement unlocks at chapter end.

Chapter 6: The Alley
Achievement: Complete Chapter 6
The penultimate chapter. The tension ramps up and the pieces of the mystery begin falling into place. Again, purely dialogue-driven. Read through and let it play out. The achievement unlocks automatically.

Chapter 7: The Woman
Achievement: Complete Chapter 7
The finale. Jack confronts Lilly and the truth behind the murders is revealed – and it goes somewhere you may not have expected from what seemed like a grounded detective story. Without spoiling it: the game takes a supernatural turn that recontextualizes everything that came before. The chapter and the game conclude with Jack sealing the threat inside his office mirror. Achievement unlocks, credits roll, 100% complete.

Achievement Summary

All 7 achievements follow the exact same structure – complete the chapter, get the achievement. No choices affect them. No chapter can be failed. The table below sums it up:
Chapter 1: The Banker – Unmissable, story-based
Chapter 2: The Park – Click muddy footprints + burn marks
Chapter 3: The Police Chief – Unmissable, story-based
Chapter 4: The Docks – Click cigarettes + purple fabric
Chapter 5: The Mayor – Unmissable, story-based
Chapter 6: The Alley – Unmissable, story-based
Chapter 7: The Woman – Unmissable, story-based

Final Word

The Monster Inside is one of the cleanest 100% completions available on Steam. No grinding, no difficulty spikes, no cryptic hidden achievements requiring a second playthrough. You sit down, you read a short noir story, you click a few things when prompted, and fifteen minutes later you're done with a perfect completion rate.
If you're hunting for easy achievements, this belongs on your list. And if you're a fan of noir in any form, the story itself is worth the minimal time investment. Either way you're not going to regret it.