energy transfer point
linking this device
to the power source.
Can you tap into it?
If I can determine the frequency
at which this device operates,
I might cause it to function for us.
And get us out the same way
we were brought in.
I would say so.
Then I'd say proceed.
You are called captain.
You are responsible
for the lives of your crew.
Is this correct?
It is.
We find it necessary
to have the cooperation
of one of your men in our efforts.
We will not cooperate.
When we resume our interrogations,
you will decide
which of your men we shall use.
It is essential.
There's an 87% chance
that the doctor will die,
and while Commander Spock's life
is not in danger,
the possibility is 93%
that he will suffer brain damage,
resulting in permanent insanity.
How's it coming, Spock?
I do not know, Captain.
I begin to understand
its operating principles,
but that's all.
It won't be long
before they come back.
Find out how that thing works
and soon.
Take it easy, Bones.
Men weren't intended
to live this far underground.
It's just not natural.
And space travel is?
Some men spend
the majority of their lives
in mines beneath the surface.
I'm a doctor, not a coal miner.
I've recorded my principles and theories
on the tricorder, Doctor.
Should the Viansreturn,
there's sufficient data
for you and the captain
to complete the adjustments.
I'm not a mechanic.
I couldn't get that thing to work.
Possibly not,
but you and the captain together
will be able to do so.
In any case, Spock,
you're the logical one
to leave with the captain.
The decision's mine.
If there are any decisions to be made,
I'll make them.
If and when it becomes necessary.
I don't need any.
I'm still chief medical officer.
I'll tell you what you need
and when you need it.
Would you rather have the bends?
That's it.
Just lie down and relax.
How long will he be asleep, Doctor?
Between the emotional strain
and that attack of bends,
he's in pretty bad shape.
I'm not criticizing your action, Doctor.
On the contrary,
I'm quite grateful for it.
The captain will be spared the strain
of making so difficult a decision.
You have simplified
the situation considerably.
How?
While the captain is asleep,
I am in command.
When the Vians return,
I shall go with them.
If I hadn't given him that shot--
Precisely.
The choice
would have been the captain's.
Now it is mine.
Your action is highly unethical.
My decision... stands.
Not this time, Spock.
The choice has been made.
You stay here with my friends.
They'll take care of you.
Do you understand?
Come, then.
Doctor,
please understand that
if there was any other way
to accomplish our purpose...
Get on with it.
Why did you let him do it?
I was convinced
in the same way you were,
by the good doctor's hypo.
Anything?
Hmm.
A most unusual device.
It is a control unit,
but not a control mechanism.
It is not a mechanical device.
What exactly is it?
This control is attuned
to one electrical pattern of energy,
the pattern produced
by the mental impulses
of the person who possesses it.
It is activated
solely by mental commands.
Can you adapt it, reattune it
to fit our brain pattern?
I shall attempt to do so.
However, it is not possible
to adjust the control
to fit more than one pattern at a time.
I am most familiar with my own pattern.
Therefore, with your permission--
Do whatever you have to
to make it work.
What disturbs me is
why the Vians let us keep it.
Fascinating.
They must have known
we were capable of
comprehending this control
and making use of it.
And that we would use it to escape.
The only logical assumption
is that they wish to let us go.
And they keep McCoy.
That is evidently
their intention, Captain.
Somehow,
you're the crux,
the focal point of all this.
Even before we got here,
she was a prisoner.
They didn't hurt her
or even threaten her.
Indeed, the facts would indicate
that she's essential to