Which form is correct: "in detail" or "in details"?

I want to use it while describing an algorithm. First I give a general description of an algorithm and then more detailed description.


I think

In detail

Is correct. Assuming that the context looks like this.

[After general description]

In detail, the algorithm will....

But you could always say..

Here, I describe the details of the algorithm.


"you describe the algorithm in detail" or "you describe the details of the algorithm".