The Doctor and Adric could not prevent the Master from killing Nyssa's stepmother. They were also unable to stop the Master from killing her father Tremas (by transferring his essence into Tremas' body) which left Nyssa orphaned in her young adulthood.
They say the companion is supposed to act as an effective audience surrogate, however Nyssa went above and beyond in this aspect; after all, she constantly fell asleep during the soul-drainingly boring episodes like Four to Doomsday and Time-Flight to represent the feelings of the viewers at home.
The Doctor is moved by this noble gesture and parts saying that he thinks she is very brave - Nyssa's deep affection for the Doctor is demonstrated at this point when she kisses the Doctor goodbye.
Fivey confirmed for having smoked dat ass.
Relationship with Peter Edit
These days the duo regularly make porn together.