{ \newcommand{\nodea}{\node[draw,circle] (a) {}
;}\newcommand{\nodeb}{\node[draw,circle] (b) {}
;}\newcommand{\nodec}{\node[draw,circle] (c) {}
;}\newcommand{\noded}{\node[draw,circle] (d) {}
;}\begin{tikzpicture}[auto]
\matrix[column sep=.3cm, row sep=.3cm,ampersand replacement=\&]{
         \&         \&         \& \nodea  \\ 
 \nodeb  \& \nodec  \& \noded  \&         \\
};

\path[ultra thick, red] (a) edge (b) edge (c) edge (d);
\end{tikzpicture}}