"So, someone asked if there is a coherent story summary in Marathon Infinity.
It is my favorite Marathon game so, against my better judgment,
I decided I would go ahead and write it."
Philtron (7 December 2020)
Philtron serialised his Marathon Infinity story summary and analysis in a series of posts on the Story forum in December 2020. You can see the links below.
Introduction covers the rationale for what will be included and not included in his analysis.
Prologue covers Ne Cede Malis and also Infinity's conditions for success.
Chapter 1: Despair, Part 1/2 covers Rise Robot Rise and Poor Yorick.
Chapter 1: Despair, Part 2/2 covers Confound Delivery and Aie Mak Sicur.
Chapter 2: Rage 1, Part 1/2 covers Acme Station, Post Naval Trauma, and Where Some Rarely Go.
Chapter 2: Rage 1, Part 2/2 covers Thing What Kicks... and Carrol Street Station.
Chapter 3: Rage 2 covers Naw Man He's Close, Foe Hammer, Hang Brain, and You're Wormfood Dude.
Chapter 4: Envy covers the levels from By Committee to Aye Mak Sicur.
It is important to read his introduction first, note what he is not covering and familiarise yourself with the terms "diegetic" and "non-diegetic". This will help you understand Philtron's point of view.
His full story summary and analysis can be read in a google drive document at this link. This is more up-to-date than the posts above as he updated his google drive document ""here and there"" after he posted.
You can also download a PDF version from the Story page here (just in case the google drive document is no longer available).
Philtron is no stranger to analysing Marathon Infinity. Back in July 2012 he posted a lengthy analysis of By Committee.