The poem begins with the speaker lamenting the huge task before him (memorializing his friend), and then invoking the muses. Then, the speaker reminisces about how the speaker and a guy named Lycidas were shepherds together. Sadly, it turns out Lycidas is dead.
Then, the speaker starts to address a series of figures from the Ancient world – nymphs, muses, you name it – and asks them all where they were when Lycidas drowned. But before he gets too accusatory, he realizes that thinking about how Lycidas could have been saved if someone had intervened is pointless. His friend is gone, and all the hard work he put in on earth is worthless, because he died before he could achieve fame.
Enter Apollo. Yep, Apollo. He's always sticking his nose in where it doesn't belong. Apollo (the poem calls him by his Roman name, Phoebus) tells the speaker to cool his jets. He reminds the speaker that fame on earth isn't nearly as awesome as life in heaven, and that life in heaven is where the real fame happens.
But the speaker isn't done spreading the blame. He wants to find out who was watching over Lycidas when he drowned. Who dropped the ball? This is when St. Peter shows up and gives a stern speech about unworthy shepherds, which we soon realize is actually about unworthy clergy members in the Church of England, who lead their flocks, or congregations, astray. The poet apologizes for the poem's digressions – apology accepted – and moves on.
Returning to the pastoral mode, the speaker asks the valleys to send all their flowers to adorn Lycidas' coffin, even though he knows Lycidas is sunk somewhere beneath the ocean, so no coffin actually exists. The poem shifts gears at the end, suggesting that Lycidas isn't really dead, because he has been reborn in Heaven, where all the saints entertain him. Things are looking up: "Tomorrow to fresh woods, and pastures new" (193).