Plotting functions and sub-functions

I am having troubles with plotting restrained functions. Here is my latest
attempt:
 
1. Define my function:
     g(x,t):= 1/[(x-t)^2+1];

2. Get a new function by setting t=1:
      g1(x):=g(x,1);

3. Notice that the new function is enclosed in square brackets:
    
4. (gnuplot) Plotting does not work: nothing being displayed

5. As g1(x) is taken out from brackets, into h1(x):
     h1(x):=part(g1(x),1);

   finally it can be plotted:  
   plot2d([h1(x)],[x,-4,4]);

I am using Maxima - version 5.15.0, lisp cmucl

What is wrong?

Thank you
--
Pol