Grigory was a medical doctor who was also a member of "Tranquil Repose Freedom Fighters", a group who intended on freeing their loved ones from Tranquil Repose. He was a friend of Natasha Stengos who was also in the group.
Grigory was a nervous man who was afraid of death on account of the fact that when they open him, he'll know the name and function of each organ that would plop out. He tried to steady himself with drink.
When Natasha couldn't retrieve her father, Arthur Stengos, from Tranquil Repose through the Courts, he helped her brake in and attempt to steal his body. He was against her having killed a guard, however. They found Stengos had been taken from his casket and discovered him mutated and being turned into a Dalek. After Natasha killed her father upon his request, they were captured and interrogated by Takis and Lilt, the security personnel.
The Doctor freed them and when they showed him the Dalek experimentation room, he planned for them to destroy the room and meet him at the reception area. When a Dalek appeared, they tried to flee but the Dalek exterminated Grigory and Natasha before self-destructing. (DW: Revelation of the Daleks)