[Vocabulary] What is the meaning of "Party line" in this sentence?

[Farshad.021]

Hey guys, in a newly released TV series called "izombie" there is a party in a boat but something happens and a girl turns into a zombie.
Now, her partner is talking to her and says:
Everyone knows the party line for the Lake Washington massacre. Drugged-up college kids. Violent fight breaks out. The only survivors are the ones smart enough to jump ship before the fire started.

Does "party line" here mean "every one knows about the lake Washington massacre"?

 

[SoothingDave]

The party line is what the party (think of the ruling party in a government, especially a one party dictatorship) holds to be true and what all good party members will say.

 

[MikeNewYork]

In this case, I think "party line" refers to what is generally believed to be true.

 

[SoothingDave]

In this case, I think "party line" refers to what is generally believed to be true.

Yes, it is the "correct" thing to say. You deviate from the party line at your own peril.

The usage is surely metaphorical. There is probably not an actual "party" in this case.