Catastrophe Available now on Amazon

Chemistry.

Most TV couples either really have it or don’t have it at all. It’s an elusive quality. Kyle Chandler and Connie Britton had tons of it on “Friday Night Lights,’’ for example. So did Amy Poehler and Adam Scott on “Parks and Recreation.’’

Rob Delaney and Sharon Horgan have fantastic chemistry on “Catastrophe,’’ the Amazon comedy that they also write, which just dropped its six-episode second season. As Rob and Sharon, who decide to make a go of their relationship in London when she gets pregnant after a quick fling, the pair are great together.

They’ve got a yin-and-yang tension going on, in that she is a brittle and barbed Irish woman and he is a gentle giant from America. But then they are also cut from the same cloth, humor-wise. They’re both able and eager to climb out of difficult and explosive conversations — about sex, about money, about parenting — with the help of warped jokes.

The story line on “Catastrophe’’ isn’t very flashy. He’s dealing with work stress, she’s dealing with dissatisfaction with the mommy lifestyle and the child-obsessed mothers she has to socialize with — she calls them “mombies,’’ because they are zombie-like in their need to talk only about kids.

But the passionate, silly, oddball connection between Rob and Sharon floats the show. It’s lovely. Along with some good supporting characters, including Carrie Fisher’s mother-in-law-from-hell, Rob and Sharon’s relationship makes “Catastrophe’’ something to see. Try it.

Matthew Gilbert can be reached at gilbert@globe.com. Follow him on Twitter @MatthewGilbert.