Illegitimate Frequency Tracer

A palm-sized energy emitter concealed within the Doctor's biological barrier, its irregular pulse detectable only by Sontaran sensors. The device is initially deployed by Stor as a compact, angular tracer with etched Sontaran runes, featuring a segmented display and a retractable probe. It emits low, pulsing hums and erratic energy bursts while attempting to detect human life signs or trace energy sources through the Doctor’s adaptive defenses. The tracer is later repurposed by Kelner in the ancillary power station to triangulate the Doctor's companions from three levels below, overriding its original tracking function. Its unsanctioned signal disrupts Vardan systems, revealing its illegitimate design through erratic energy signatures.

3 appearances

Appearances in the Narrative

When this object appears and how it's used

3 moments

S15E26 · The Invasion of Time Part 6

Kelner rigs corridor to seize power component

The Sontaran tracer detects the Doctor's companions' location three levels below after Kelner positions it for operation. The device's erratic bursts disrupt prior tracking locks and reveal the companions' hiding place, enabling the Sontarans to close in on their quarry and escalate the pursuit.

Before: Concealed within the Doctor's biological barrier, functioning erratically to track his presence

After: Repurposed by Kelner to triangulate the Doctor's companions from three levels below, its signal now aligned with the needs of the Sontaran mission

View full event

S15E24 · The Invasion of Time Part 4

Vardan detection of Doctors trap exposed

The Illegitimate Frequency Tracer— camouflaged within the Doctor’s ceremonial surrender— abruptly switches from dormant to active mode, emitting an unsanctioned pulse detectable by Vardan sensors. Its covert energy signature pulses erratically, breaching containment and broadcasting the Doctor’s hidden gambit across the Panopticon’s surveillance network, instantaneously betraying months of infiltration.

Before: Concealed within the folds of the Doctor’s surrender, powered in standby mode, undetected by all prior scans

After: Activated and broadcasting, triggering full-alert protocols in the Vardan Leader’s systems and exposing the Doctor’s deception across Gallifrey

View full event

S15E26 · The Invasion of Time Part 6

Sontarans uncover TARDIS vulnerability

Stor’s tracer on his comm. unit detects energy irregularities caused by the Doctor’s biological barrier. Initially designed to track life forms, the device fails to penetrate the barrier’s adaptive defenses but is repurposed by Kelner to identify the ancillary generator as the barrier’s power source, turning technical failure into strategic insight.

Before: Functional tracer in Stor’s possession, calibrated for biological scanning but ineffective due to the Doctor’s barrier.

After: Same device shifts function through Kelner’s tactical adaptation, now becoming a tool for indirect infiltration.

View full event