Hello Jan,
Open up /wp-content/themes/infocus/lib/includes/template-blog.php and find lines 231 - 237 which should look like this..
<?php if($teaser_text) { ?>
<p class="portfolio"><?php echo $teaser_text; ?></p>
<?php } ?>
<?php if(!$read_more_disable) { ?>
<span><a class="button_link" href="<?php the_permalink(); ?>"><span>Read More</span></a></span>
<?php } ?>
You will want to add a line inbetween like this..
<?php if($teaser_text) { ?>
<p class="portfolio"><?php echo $teaser_text; ?></p>
<?php } ?>
<?php the_excerpt(); ?>
<?php if(!$read_more_disable) { ?>
<span><a class="button_link" href="<?php the_permalink(); ?>"><span>Read More</span></a></span>
<?php } ?>
This could throw your categories out of balance so you might want to surround it with a div like this..
<div style = 'overflow: hidden; width: 100px; height: 50px;'><?php the_excerpt(); ?></div>
Play around with the width and height until you get something you like.