Derive from a base class but not include a condition in the base class's method

The current code looks like this:

public class Details
{
    Public void Populate()
    {
         WriteChapterDetails();
    }

    public void WriteChapterDetails()
    {
       if ( includeHighDetails)        
       {
         \\Do something
       }

       if (includeLowDetails)
       {
         \\Do something
       }
    }
}

I now want to write a new class named HighDetails which will be copy of the Details class except I don't want it to go to the if (includeLowDetails) condition.

I am thinking of deriving a class from Details class like:

public class HighDetails()
{
  Public void Populate()
    {
         WriteChapterDetails();
    }

    public void WriteChapterDetails()
    {
       if ( includeHighDetails)        
       {
         \\Do something
       }
}

The Details class is a huge class and I don't want to repeat all the methods in the HighDetails class. I want to derive from the Details class and somehow not include the LowDetails. How can I do that?