This will be ffg's answer to the pathfinder card game, with the campaign mode being equivalent to the legacy type of gameplay found in pathfinder.
I thought I should explain this a bit more, for those who are not familiar with the pathfinder card game.
Pathfinder is the marmite of LCG's, you either love it or hate it. It has the greatest framework of any card game but then scenario and card design was handed off to a bunch of brain dead monkeys.
Each player has a hero, with attributes, skills, multiple upgrade paths (for levelling up) and their own deck construction rules. Up to 6 players can take part, forming an adventuring group, with the game scaling to the number of hero's in use.
An adventure path (deluxe + 6 chapter packs) is made up of 33 scenarios that are played in order, and form one long story. The scenarios get more difficult, a beginning hero would stand no chance against a CP6 scenario, experience must be gained and powerful items acquired first.
A scenario is made up of X locations, scaled according to the number of players, and a turn limit to keep up the pressure. The hero's move to different locations and investigate, finding items & recruiting allies, as well as fighting enemies and overcoming obstacles.
What makes the game great is that it is a legacy card game, the events of one scenario effect the following scenarios and characters evolve (or die). Whenever you find an item it's added to your deck, when you make an ally the card goes in your deck, when you use a one use item (potion) or an ally dies you lose that card from your deck. At the end of the scenario you remove excess cards from your deck, changing your deck each time you play. Each card in your deck becomes part of the story, whenever a thief makes off with you favourite sword you'll feel that hurt for a long time.
When a hero dies they go back in the box and cannot be used for the rest of the adventure path, you have to pick a new hero.
When I think of a single investigator game with a campaign mode I imagine it being a legacy storytelling game like pathfinder.