The Zygons returned in 2013 in "The Day of the Doctor", the 50th anniversary episode of the programme. The episode hints the stellar explosion (said to have destroyed their homeworld in the 1975 serial) was an effect of the Time War. A squad places themselves in suspended animation in Elizabethan England, planning to awaken in 2013 to infiltrate the Tower of London's Black Archive disguised as UNIT members. The scheme is foiled by the intervention of the Tenth Doctor, the Eleventh Doctor and the War Doctor. When UNIT is overrun by Zygon doppelgangers, Kate Lethbridge-Stewart threatens to detonate a nuclear device to prevent Zygon access to UNIT's storehouse of alien technology. The Doctors successfully negotiate a truce between the two species.