When I ran the H1-3 campaign I interpreted the PoL as follows-
PCs Level 1-
Started with a Goblin attack on Fallcrest- large band of the creatures attacking the city, one of many roving bands (Bloodreavers)- PCs only had a bit part to play in the action but got scared about the roads.
This resulted in Fallcrest closing the gates, and road travel being difficult in the extreme, large armed caravans only.
PCs had to travel to Winterhaven (a messenger gets through), a few minor encounters, mostly scares- an extended Skill Challenge, followed by the Kobold bandits from H1 hitting early in the game- almost a seperate entity to the rest of the scenario that need to be dealt with first.
PCs complete H1 and manage in the process to free up the road to Fallcrest- they hear about Karavakos.
PCs Level 4-
PCs head out to Thunderpsire, again attacked en route- bandits mostly. I added a fortified Inn on the road (on the spur to Thunderspire). The PCs encountered the inhabitants of the Inn en route to the place, being chased by more Goblins and worse.
PCs have to retake the Inn, and realise in the process that the Goblins in question are more Bloodreavers (they represent the scourge of the Vale- HQ Thunderspire).
PCs then have to hold the Inn as it is beseiged by another group of Dire Wolves, Ogres and more nastier Goblins (and worse). They hold the Inn till the Fallcrest road patrol turns up (heavily armed), the Inn is held.
PCs into Thunderspire, which I levelled up and made the Blooreavers a whole lot nastier (but a cover for the Duergar, and ultimately a cover for Paldemar who manipulated the Bloodreavers et al for... Karavakos). PCs win through- the Vale is a little less PoL.
PCs Level 8-
The lull before the storm- the PCs and the Vale are rescued, much good stuff.
The PCs head back to Fallcrest- and are dragged in to see the Markelhay's, envoys from the Feywild have come across to beg for help- something terrible is happening in the Fell version of Fallcrest (Fellscarp). PCs get tangled up in a strange adventure when the Feywild emmisary is kidnapped in Fallcrest.
Detective style scenario follows, this after one of the PCs slept with the Princess and therefore has a personal reason to want her back- you should have seen his rolls for the Skill Challenge (kidding).
Eventually in the sewers of Fallcrest PCs start encountering many nasties and at the root of it all an Aboleth, which turns out to be a shape-changing Aboleth (and the Princess the PCs are looking for- yes one of the PCs had sex with an Aboleth).
In the final confrontation the Aboleth begs his/her/its PC lover to join with it and rule the Vale, the PC is less keen. The Aboleth is killed and a bunch of illusions fade out- the Aboleth curses the PCs, states its master is here and dies.
Spectral/real/fey plants begin to grow at incredible rate- bursting through the walls of the sewers- the entire place collapses and a Skill Challenge to get out and back to the surface follows.
PCs escape the sewer to discover the entire city of Fallcrest has been crushed/broken/destroyed etc. by this strange plant- the plant turns out to be part Fey part Shadow.
All the citizens of the city have been captured by the quick growing plants- grabbed, injected and placed in a coma, the plants keep the citizens alive (symbiotic)- see Matrix etc..
The PCs hack their way to the Septarch's tower, en route encountering large Preying Mantis, on the docks large water scorpions and terror shrimp (or similar), a gigantic beetle and latter a colossal Slug- which was just a great fight, the thing had a bite that did something like 50+ damage, and an acid style spit- just lovely. All creatures combine shadow and fey traits.
The PCs get to the Septarch's tower, Nimozaran is still alive- the tower is impervious to the magic.
Scrying discovers that the entire Nentir Vale is choked by this Fey/Shadow plant.
The PCs don't know what to do- then the storms start (think the lightning strikes from the last War of the Worlds film)- massiving rolling clouds black out the sun.
A Twister of incredible size rips through Fallcrest, not doing any damage but instead sending the bodies of the citizens spiralling up in to the black.
Then silence followed by a pulsing light within the black above- the black clouds clear a little and floating above the city is the Pyramid of Shadow.
As it turns out the Pyramid was built by Nimozaran who in my game is considerably older than the PCs think- this has been hinted at many times. It was made in conjunction with a mad clan of techno dwarves who built the Dwarforged. One of the PCs has discovered he may be a Dwarforged some time ago.
Nimozaran's teleport circle comes alive when the PC is about, the PC probably is a Dwarforged, regardless he can teleport in to the Pyramid.
The PCs are the only hope for Fallcrest and the Vale, this is my interpretation of the Paragon leap from heroes known by a few to paragons lauded by all the land.
PCs Level 9-
The PCs head up to the Pyramid and kick ass, several of the groups in the Pyramid have already been worked in to the narrative previous- the Feywild (Arboreans) have been known enemies for the last x levels, same for the human bandits up there (lead by a Dragonborn I think, this guy was the ex-head of the Fallcrest guard who tried to kill Markelhay one-day- possessed by the Tiefling king of the Pyramid-Karavakos who has been foreshadowed since forever).
PCs eventually defeat Karavakos, having rescued the Dragonborn (and helped along several of their individual stories- one of the PCs had been playing with the Far Realm when he was young and was responsible for the destruction of the monastery he was studying at- Karavakos again).
Pyramid destroyed- PCs teleport out, the plants wither and die, the citizens reappear and as it turns out the 8 days the PCs spent in the Pyramid equate to 8 months of shadow for the entire Vale.
From there the plot gets complicated, but you can see what I mean- PoL means just that- fight for your life, not even the cities are safe.
At least that was my version.
Sorry for long post but that was my interpretation, I'd tell you about the Paragon stuff but quite frankly I'm going to be using some of it in my present campaign and I don't want my present PCs to read it here. Needless to say the Paragon version of PoL sees the entire Vale transformed and threatened et al.
My latest campaign takes place after The Time of Shadow, the new PCs have just played HS1- Kiris Dahn/Gorizbadd (the ruined town in the module) was destroyed by Goblins (and the plants) during the time of Shadow.
I love a good story me.
Cheers Goonalan