Stung by the mass defection of all of its partners in London and Moscow, New York-based Coudert Brothers is exploring a possible lawsuit against San Francisco’s Orrick, Herrington & Sutcliffe, the firm that hired the partners away.

Coudert Brothers has retained Barry Ostrager, the co-head of the litigation department of Simpson Thacher & Bartlett, to conduct an investigation into whether Orrick and the departing partners breached confidences gained in merger discussions between the two law firms.