Talmai — Addition A 13: He overhears their plot against the king and reports it.
Licence: English and apparatus CC BY 4.0 (Talmai, Wroot Press); Greek from Swete, CC BY-SA. https://talmai.wrootpress.com/rights/
Canonical: https://talmai.wrootpress.com/unit/esth-plus-01.01-13/
Source edition: H. B. Swete, The Old Testament in Greek, 19.prologue

GREEK: ἤκουσέν τε αὐτῶν τοὺς λογισμοὺς καὶ τὰς μερίμνας αὐτῶν ἐξηραύνησεν, καὶ ἔμαθεν ὅτι ἑτοιμάζουσιν τὰς χεῖρας ἐπιβαλεῖν Ἀρταξέρξῃ τῷ βασιλεῖ καὶ ὑπέδειξεν τῷ βασιλεῖ περὶ αὐτῶν·
ENGLISH (draft-awaiting-approval): and he overheard their reasonings and searched out their designs, and learned that they were preparing to lay hands on Artaxerxes the king, and he informed the king about them;

PARALLELS:
- [Motif] Rashi on Megillah 13b:10:1 (Rashi on Bavli Megillah 9a-17a) — conduit: oral. Rashi supplies the specific detail of how Mordecai understood the plot -- the conspirators spoke Tarsian -- filling exactly the gap Addition A covers with 'overheard their reasonings.'
- [Flagged] Yalkut Shimoni on Nach 1053:29 (Yalkut Shimoni on Esther (Remez 1046-1061)) — conduit: lost intermediary. Mordecai overhears the two eunuchs speaking Tarsian (which he understands from the Chamber of Hewn Stone) and learns of their poison plot — a specific mechanism of discovery matching 'overheard their reasonings and searched out their designs'; not MT (MT gives no mechanism).
- [Flagged] Pirkei DeRabbi Eliezer 50:3 (Pirkei DeRabbi Eliezer 49-50) — conduit: oral. 'ושמע שני סריסי המלך מדברים בלשון כשדים' -- Mordecai (who knows seventy tongues) overhears the eunuchs' private plot in a foreign tongue, matching the plus's distinctive 'overheard their reasonings and searched out their designs' against MT's passive 'the matter became known.'
- [Verbatim] Tosefet le-Esther, בגתן ותרש (Tosefet le-Esther (he.wikisource editorial page: Additions to Esther in Hebrew)) — conduit: medieval retranslation. 'וירא אותם מתלחשים והכיר עצתם וחשב שהם חושבים לשלוח יד במלך' renders Addition A's distinctive 'overheard their reasonings and searched out their designs' against MT's passive formulation.
- [Flagged] Otzar Midrashim, Midrashim on Megilat Esther, Midrash on the Book of Esther 4 (Otzar Midrashim: Midrash on the Book of Esther) — conduit: lost intermediary. Mordecai overhears the two eunuchs conspiring in a foreign tongue ('Tarsian'), knowing seventy languages, and reports it -- an explanation of how Mordecai learned of the plot that MT never gives, matching the plus's 'he overheard their reasonings and searched out their designs.'
- [Flagged] Sifrei Aggadah on Esther, Midrash Panim Acherim, Version II 2:18 (Sifrei Aggadah on Esther: Midrash Panim Acherim, Version II) — conduit: lost intermediary. Mordecai, knowing seventy languages, actively overhears the conspirators' private plan and investigates it before reporting -- the same distinctive detail of active overhearing/investigation ('he overheard their reasonings and searched out their designs') that MT's bare 'the matter became known to Mordecai' lacks.
- [Motif] Aramaic Targum to Esther 2:22 (Aramaic Targum to Esther (Targum Rishon)) — conduit: Aramaic. The targum supplies the mechanism MT lacks -- Mordecai understood the plot because he knew seventy languages -- matching the plus's account of how he overheard and construed their designs.
- [Motif] Rashi on Esther 2:22:1 (Rashi on Esther) — conduit: lost intermediary. Rashi gives the same seventy-languages mechanism (they spoke in Tursi, not knowing Mordecai understood) for how he overheard the plot.