Original: Soon Publius arrives to arrest Sextus, bearing the news that it was one of Sextus's co-conspirators who dressed himself in Titus's robes and was stabbed, though not mortally, by Sextus.
Simplified: Soon Publius arrives to arrest Sextus, bringing the news that it was one of Sextus’ friends who dressed himself in Titus's robes and was stabbed by Sextus, but he did not die.