Trapped on the Sense-Sphere, Ian is dying from the illness that has been killing the Sensorites and the Doctor tries to find a cure.
| Name | Type | Role | |
|---|---|---|---|
| Peter R. Newman | Writer | ||
| Joe Greig | Guest Star | ||
| Arthur Newall | Guest Star | ||
| Ken Tyllsen | Guest Star | ||
| Peter Glaze | Guest Star | ||
| Stephen Dartnell | Guest Star | ||
| Bartlett Mullins | Guest Star | ||
| Ilona Rodgers | Guest Star | ||
| Eric Francis | Guest Star | ||
| Mervyn Pinfield | Director |