The following program includes descriptions of graphic and sexually explicit violence.

This show may not be suitable for those affected by such descriptions or for young listeners.

Parental discretion is advised.

Previously on Stranglers, five women were strangled in Boston in the summer of 1962.

The women were all older, between 55 and 75.

They were left in obscene positions with the flowing bows and knots.

Then in December 1962, two more victims were found, both strangled in their own homes

with pieces of their own clothing as before.

But this time, the women were much younger.

Sophie Clark and Patricia Bissett were both in their 20s.

It's very, very unusual for a sexual murderer of elderly women to change targets to a much younger victim.

I've not seen it with any of the serial offenders that I'm familiar with.

The first five women had been sexually abused with objects.

In the murders of Clark and Bissett, there was no evidence of such abuse.

The difference suggested a copycat strangler or stranglers.

Last episode, we met Adele Roof, the previous tenant of Bissett's apartment.

Adele told us that just months before the murder, a strange man had been lingering around her door.

At first, I wasn't nervous, but then I looked down and he was performing a sexual act on himself there at the door.

Adele saw him several times.

She even tailed him once into a dangerous neighborhood and reported the address to the police.

But with all the thousands of tips in the strangler investigation,

it seems police lost track of Adele's lead.

...