Question: I am writing a document in which I would like to include table of contents, after which I will write a prologue.

The issue is that the second page of the chapter, has the header of the ToC, as seen in the following image[![enter image description here](https://i.stack.imgur.com/RDp8k.png)](https://i.stack.imgur.com/RDp8k.png)

Any idea on how to add the proper header?

A sample code follows

```
\documentclass{book}
\usepackage[Conny]{fncychap}%Options: Sonny, Lenny, Glenn, Conny, Rejne, Bjarne, Bjornstrup
\UCTfalse
\usepackage{blindtext}

\begin{document}

\tableofcontents

\chapter*{Prologue}
\blindtext[5]
\end{document}

```

Answer: 
suppressing the chapter name with `\chapter*{}` causes the headers not to update. You can change that by adding `\markboth{Prologue}{}`.

```
\documentclass{book}
\usepackage[Conny]{fncychap}%Options: Sonny, Lenny, Glenn, Conny, Rejne, Bjarne, Bjornstrup
\UCTfalse
\usepackage{blindtext}

\begin{document}
    \tableofcontents
    \chapter*{Prologue}
    \addcontentsline{toc}{chapter}{Prologue}  % if you want to add the Prologue to TOC
    \markboth{Prologue}{}                     % to change the header despite \chapter*{} command
    \blindtext[5]
\end{document}

```

Here's the result:  

[![preview](https://i.stack.imgur.com/TkJFt.png)](https://i.stack.imgur.com/TkJFt.png)

Hope this helps :)

Edit: note that you will have to do this for every chapter you suppress with `*`, if you want it to change the headers, not just after the TOC.
You can use `\frontmatter`, `\mainmatter` and `\backmatter` commands and place the whole frontmatter inside a "group" (`\begingroup` and `\endgroup` commands) with a `\pagestyle{plain}` command just after `\frontmatter`:

```
\documentclass{book}
\usepackage[Conny]{fncychap}%Options: Sonny, Lenny, Glenn, Conny, Rejne, Bjarne, Bjornstrup
\UCTfalse
\usepackage{blindtext}
\title{Test}
\begin{document}

\maketitle
\begingroup
\pagestyle{plain}
\frontmatter
\tableofcontents
\chapter*{Prologue}
\blindtext[5]
\endgroup
\mainmatter
\chapter{Introduction}
\blindtext[5]
\backmatter
\appendix
\chapter{App1}
\blindtext[5]
\end{document}

```

Check the headers and footers in the result of the above code to see if everything is as expected from you.