I remember the first time I crept onto the Bio-Research walkway: a single misstep and the whole run collapses. You can feel the map compress around that one objective—grab the sample, analyze it, get out. I’ll walk you through a single, reliable run so you don’t have to learn the hard way.
I’ve finished Selection Pressures 4 enough times to know where people stall. You and I will shave minutes off messy attempts and dodge the common traps that cost lives and resets.
Most players pause on the approach — Marathon Selection Pressures 4 Contract walkthrough
The contract breaks into three clear tasks. Treat them as a single chain: one error forces a complete redo.
- Acquire the active contagion sample in Bio-Research
- Analyze the sample at the analyzer in Quarantine
- Download the results and exfil safely
Stairwells and sightlines matter — How to acquire active contagion sample in Bio-Research
The Bio-Research POI sits in the north. Take the stairs up to the second-floor walkway and follow it to the end — it doesn’t matter where you join the path, but where you finish matters. The walkway feels like a spine; control it and you control the room.
Where is the contagion sample in Bio-Research?
Enter the building shown above, go into the first room on your left, and you’ll see the sample highlighted for scan. The game highlights objective items, but enemies often camp the approach: clear the doorway first, then approach the sample and pick it up.
Doors and enemy patrols teach you timing — How to analyze the sample using an analyzer in Quarantine
Quarantine sits southwest on the map; the analyzer is inside the main building, upstairs. Enter the main room and the analyzer will glow — the game points it out, but the area is large and full of enemies. Bring a plan: cover angles, clear patrols, and keep the sample in your inventory until you reach the terminal.
How do I analyze the sample in Quarantine?
Use the stairs to the second floor, place the sample into the analyzer’s inventory, and start the process. The analyzer triggers enemy waves—UESC hostiles will swarm to slow your progress. Kill the waves, hold the room, then interact to download the data. If you’re solo, prioritize corners and chokepoints; in a fireteam, assign one player to watch the stairwell and another to manage pressure at the door.
Platforms like Bungie.net, Reddit threads, and Discord channels often reveal spawn tricks and loadout recommendations. On PC (Steam), controller users and mouse-and-keyboard players will both find value in an automatic weapon for close work and a precision option for overwatch. Mentioning Bungie here matters because their update notes sometimes change enemy count or spawn timing—check patch notes before runs.
Doors open, alarms ring — How to download the analysis results and exfil
You’ll notice the map compress after the download starts: enemy density spikes and exfil windows shrink. Treat the extraction like a timed sprint, not a siege.
How do I exfil after analysis?
Once the download completes, interact to collect the file and move to the extraction point. Kill the remaining UESC forces as they converge. If you die now, the contract resets to step one, so play cautiously. Use cover, bait grenades to clear clusters, and use your super only when you can clear a path to the exit.
If you want live advice, post a short clip to the Marathon subreddit or a Discord lobby—players there often share exact spawn timings and a quick tip can save a run. For gear, prioritize survivability mods and ammo economy during the analysis phase; aggressively chasing kills in the Quarantine usually costs the run.
Run this route a few times and the sequence becomes muscle memory: grab the sample, hold the analyzer room, download fast, and exfil. The exit beacon behaves like a lighthouse in fog—follow its light, but don’t sprint blindly toward it.
Ready to try a clean run and steal the completion from the chaos?