General :: Sed Error - Extra Characters After Command

sed '/
$/ {N s/
//}'
sed: -e expression #1, char 10: extra characters after command

I want to understand what is wrong with my command line. When I can do the some of following in a script but not in a command line. I have been working through the tutorial at [URL]. When I got stuck at the section Working with Multiple Lines. These script works fine.

#!/bin/sh
sed '
# look for a "#" at the end of the line
/#$/ {
# Found one - now read in the next line
N
# delete the "#" and the new line character,
s/#
//
}' file

In my case I am looking for or return ^M.
#!/bin/sh
sed '
# look for a "#" at the end of the line
/
$/ {
# Found one - now read in the next line
N
# delete the "#" and the new line character,
s/
//
}' file

The problem is when I try to convert it to a single line shell command it gives me an errors.
sed '/
$/ {N s/
//}'
sed: -e expression #1, char 10: extra characters after command
sed '/
$/{N s/
//}'
sed: -e expression #1, char 9: extra characters after command
sed '/
$/{Ns/
//}'
sed: -e expression #1, char 8: extra characters after command

I want to understand what is wrong with my command line. When I can do the following in a script but not in a command line. I have created a sed script to do the work I want.
cat test.sed
#!/bin/sed -f
/
$/ {
N
s/
//
}