。
Achilles was invulnerable except for his heel.
Literal
Achilles [topic-は] heel [object-を] except-[topic-は], immortal was.
The Japanese version of the Achilles' heel myth. Note the double-particle combination ~を除いては — を marks what is excluded, and the emphatic は flags that this is the single exception being singled out. 不死身 (ふじみ) literally 'not-dead-body', functions as a na-adjective/noun meaning 'immortal' or 'invulnerable'.