Rishe has kept a certain activity of hers secret from Arnold, but when he appears right in front of her, there's no escaping his notice. Later she learns that Michel believes Arnold fulfills every condition necessary to conduct a particular experiment.
the only question is how 
to deal the final blow.
فالسُّؤال الوحيد هو كيفيّة توجيه الضّربة القاضية
La question est
quand porter le coup fatal.
L'unica domanda è come infliggere il colpo finale.
a dúvida é como dar o golpe final.
остаётся решить, как её добить.