"Don't worry," the Master had said as he made his escape, "I'm sure you'll have enough time to rescue the... undoubtedly charming Miss Jovanka." But there had been—as there always was—something sinister in the way he said it, nagging at the back of the Doctor's mind as he raced through the slowly self-destructing scientific base.
When he burst into the secure lab—a converted warehouse which had housed the institution's most sensitive projects, well, until today, that is—he understood. On one side of the cavernous room stood Tegan, struggling desperately against the handcuffs that bound her to a metal girder.
On the other side—exactly the same. Same slight figure, same short hair, same abstract-painting blouse, same uncomfortable-looking handcuffs, same voice shrieking "Doctor, get a move on!"
"I thought I told you to go back to the TARDIS!" he shouted, turning in confusion from one Tegan to the other.
"I was looking for you, idiot!" replied both of them, almost in unison. He thought one of them had spoken a millisecond before the other—one must be the real Tegan, the other an imposter imitating her—but he'd been turning his head and couldn't tell which.
"No need to say thanks or anything," added the Tegan on his left. The Doctor subconsciously moved towards her.
"Ignore her! She's a fake!" shouted the Tegan on the right. An ominous rumble and a fall of plaster from the ceiling reminded him that they didn't have long to get out of here.
"Listen," said the one on the left. "She's the fake, the Master set up a solid hologram projector—or something like that. You don't have to try to save her, she's not real. Get your toothpick or whatever it is, pick this lock and let's get out of here!"
The Doctor fumbled for the hairpin in his pocket—not a toothpick, shouldn't she have known that?—and hesitated. "Not her!" insisted the woman on the right. "Not her! Me!"
Another rumble and a crash from the corridor. They really didn't have long.
He took a step back, staring at each Tegan in turn. With the Master involved, the consequences of setting the wrong woman free could well be much worse than the embarrassment of having fallen for a hologram. He wouldn't put it past his old enemy's diabolical sense of humor to conceal a dangerous explosive or a psychic attack to be triggered by the wrong choice. But how was he to decide? There was no visible difference whatsoever, even down to the smudges of soot and dirt she'd incurred during the day's events.
In that split second of hesitation, the Tegan on the right shrieked once more. "Doctor!" she cried. "Only you can save me!"
Before he could reply, the other Tegan screamed, "Come on, Doctor! Get us out of this!"
Us, she'd said. Suddenly, he was certain. The real Tegan thought of them as a team. The real Tegan would be the first to tell anyone that sometimes he rescued her, sometimes she rescued him, and they both needed each other.
The real Tegan was on his left.
Moving like lightning now that he was sure, he had her handcuffs open in no longer than it took her to tell him to hurry. As she stumbled away from the girder, recovering her balance, he caught her in his arms and couldn't help folding her to himself.
With a final shriek, the hologram vanished before their eyes. A pair of empty handcuffs clattered to the ground across the room.
"I knew you'd work it out eventually," said Tegan, putting her arms around him. As he took a deep breath of relief, he felt like he never wanted to let her go. His mouth brushed against her hair.
"Kiss me later," she said, releasing the embrace and taking his hand instead.
Hand in hand, just like always, they ran for the TARDIS and safety.