In Propertius’ poem, the speaker complains about his girl’s infidelity and how awful it is to see her “cocked on another man’s arm” (line 5). He seems unsure how to deal with it at first, but finally the story of Antigone and Haemon comes to mind and he thinks of suicide and death. He threatens Cynthia and says that if he dies through love, she should die too. The Beatles’ song too is about infidelity and revenge: “Catch you with another man, that’s the end, little girl.” If that happens, the speaker knows what he will do – he will pursue her (“you better run for your life”) and kill her (that’s the end). Both poems reflect the lover’s jealousy and aggressive tendencies, but one difference is that Propertius seems to have actual evidence of infidelity, while in the Beatles’ song it is just imagined.
Propertius II.8, lines 5-6, 25-28:
Can I see her cocked on another’s arm?
Will she not be called mine who was called mine yesterday?
But you won’t get away with it: you should die with me;
Your blood and mine should drip from the same sword.
Though that death of mine will be dishonorable —
a dishonorable death indeed — but you’ll die too.